Image text: The top computer champion at Seven Minutes in Heaven is a Honda-built Realdoll, but to date it has been unable to outperform the human Seven Minutes in Heaven champion, Ken Jennings.

This explanation got really long, so I'm placing it after the jump.

Ok, let's get right into it.  To understand the comic, you have to understand what the games are, so let's go (but first, the years in parenthesis in the comic are the year that the game was mastered by a computer):

Tic-Tac-Toe - (via wikipedia) Tic-tac-toe, also called noughts and crosses (in the UK, Australia, New Zealand, South Africa, India and the rest of the British Commonwealth countries), is a pencil-and-paper game for two players, X and O, who take turns marking the spaces in a 3×3 grid.

Nim - (via wikipedia) a mathematical game of strategy in which two players take turns removing objects from distinct heaps. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap.
Ghosts - I'm going to guess this board game (via Board Game Geek), but the commenters have told me that it could also be this spoken word game.

Connect Four - (via wikipedia) (also known as Captain's Mistress, Four Up, Plot Four, Find Four, Fourplay, Four in a Row and Four in a Line) is a two-player game in which the players first choose a color and then take turns dropping their colored discs from the top into a seven-column, six-row vertically-suspended grid.

Gomoku - (via wikipedia) an abstract strategy board game. Also called Gobang or Five in a Row, it is traditionally played with go pieces (black and white stones) on a go board (19x19 intersections); however, because once placed, pieces are not moved or removed from the board, gomoku may also be played as a paper and pencil game. This game is known in several countries under different names.

Black plays first, and players alternate in placing a stone of their color on an empty intersection. The winner is the first player to get an unbroken row of five stones horizontally, vertically, or diagonally.

Scrabble - (wiki) a word game in which two to four players score points by forming words from individual lettered tiles on a gameboard marked with a 15-by-15 grid.

Counterstrike - is an first person shooter video game. That doesn't make much sense does it?  The commenters suggest that it could be this backgammon variant. (via Board Game Geek)

Beer pong - (via wiki) also known as Beirut, is a drinking game in which players throw a ping pong ball across a table with the intent of landing the ball in a cup of beer on the other end.
Here's the video of the University of Illinois robot mentioned in the comic.

Reversi - (via wiki) (also marketed by Pressman under the trade name Othello) is a board game involving abstract strategy and played by two players on a board with 8 rows and 8 columns and a set of distinct pieces for each side. Pieces typically are disks with a light and a dark face, each face belonging to one player. The player's goal is to have a majority of their colored pieces showing at the end of the game, turning over as many of their opponent's pieces as possible.

Chess - (wiki) Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. Each player begins the game with sixteen pieces: one king, one queen, two rooks, two knights, two bishops, and eight pawns, each of these types of pieces moving differently.

Jeopardy - (wiki) an American quiz show featuring trivia in history, literature, the arts, pop culture, science, sports, geography, wordplay, and more. The show has a unique answer-and-question format in which contestants are presented with clues in the form of answers, and must phrase their responses in question form.
Ken Jennings, mentioned in the image text is a famous Jeopardy champion.

Starcraft - (wiki'ed) a military science fiction real-time strategy video game... the game revolves around three species fighting for dominance in a distant part of the Milky Way galaxy known as the Koprulu Sector: the Terrans, humans exiled from Earth skilled at adapting to any situation; the Zerg, a race of insectoid aliens in pursuit of genetic perfection, obsessed with assimilating other races; and the Protoss, a humanoid species with advanced technology and psionic abilities, attempting to preserve their civilization and strict philosophical way of living from the Zerg.

Poker - (wiki) a family of card games involving betting and individualistic play whereby the winner is determined by the ranks and combinations of their cards, some of which remain hidden until the end of the game.

Arimaa - (wiki) a two-player abstract strategy board game that can be played using the same equipment as chess. Arimaa was designed to be more difficult for artificial intelligences to play than chess. Arimaa was invented by Omar Syed, an Indian American computer engineer trained in artificial intelligence. Syed was inspired by Garry Kasparov's defeat at the hands of the chess computer Deep Blue to design a new game which could be played with a standard chess set, would be difficult for computers to play well, but would have rules simple enough for his then four-year-old son Aamir to understand.

Go - (wiki) an ancient board game for two players that originated in China more than 2,000 years ago. The game is noted for being rich in strategy despite its relatively simple rules. The game is played by two players who alternately place black and white stones on the vacant intersections (called "points") of a grid of 19×19 lines (beginners often play on smaller 9×9 and 13×13 boards). The object of the game is to use one's stones to surround a larger portion of the board than the opponent.

Snakes and Ladders - (via wikipedia) (or Chutes and Ladders) an ancient Indian board game regarded today as a worldwide classic. It is played between two or more players on a gameboard having numbered, gridded squares. A number of "ladders" and "snakes" (or "chutes") are pictured on the board, each connecting two specific board squares. The object of the game is to navigate one's game piece from the start (bottom square) to the finish (top square), helped or hindered by ladders and snakes, respectively.

Mao - (via wiki) (or Mau) a card game of the Shedding family, in which the aim is to get rid of all of the cards in hand without breaking certain unspoken rules. The game is from a subset of the Stops family, and is similar in structure to the card game Uno or Crazy Eights.
The game forbids its players from explaining the rules, and new players are often told only "the only rule you may be told is this one." The ultimate goal of the game is to be the first player to get rid of all the cards in their hand.

Seven Minutes in Heaven - (yes, seriously I went to wikipedia!) a teenagers' party game first recorded as being played in Cincinnati in the early 1950s. Two people are selected to go into a closet or other dark enclosed space and do whatever they like for seven minutes. Sexual activities are allowed; however kissing and making out are more common.

And finally Calvinball is a reference to the comic strip Calvin and Hobbes by Bill Watterson - (via wikipedia)

Calvinball is a game played by Calvin and Hobbes as a rebellion against organized team sports; according to Hobbes, "No sport is less organized than Calvinball!" Calvinball was first introduced to the readers at the end of a 1990 storyline involving Calvin reluctantly joining recess baseball. It quickly became a staple of the comic afterwards.

The only hint at the true creation of the game ironically comes from the last Calvinball strip, in which a game of football quickly devolves into a game of Calvinball. Calvin remarks that "sooner or later, all our games turn into Calvinball," suggesting a similar scenario that directly led to the creation of the sport. Calvin and Hobbes usually play by themselves, although in one storyline Rosalyn (Calvin's baby-sitter) plays in return for Calvin doing his homework, and plays very well once she realizes that the rules are made up on the spot.

The only consistent rule states that Calvinball may never be played with the same rules twice. Scoring is also arbitrary, with Hobbes at times reporting scores of "Q to 12" and "oogy to boogy." The only recognizable sports Calvinball resembles are the ones it emulates (i.e., a cross between croquet, polo, badminton, capture the flag, and volleyball.)

Image text: If you fire a Portal gun through the door of the wardrobe, space and time knot together, which leads to a frustrated Aslan trying to impart Christian morality to the Space sphere.

This comic was posted late and now I'm late and I'm at work so I can't do as much explaining as I usually do, but I'll do my best.  That's also why we have the best comment section on the Internet.

The basic idea of the formula and the comic are based on the books and movies of the Lion, the Witch and the Wardrobe in which a giant wardrobe contains a portal to a world known as Narnia. In the comic, someone connects an anchor to the wardrobe and throws it into the ocean which means that a steady stream of water at a velocity of 200 m/s will flow into Narnia.

The White Witch, the antagonist in the books and movies apparently won't know what hit her according to the caption.

The image text references the video game "Portal" in which you fire a portal gun into walls and etc to make "portals" that can open holes in other places so that you may portal through.

The image text also references the fact that CS Lewis wrote the Lion, Witch and Wardrobe books as a thinly veiled allegory of Christ's crucifixion with Aslan, the Lion in the title, playing Christ's part.  (Spoiler alert! Sorry!)

This is a classic xkcd based on the intersection of literature, math and video games.

Image text: If you've never had sex, this is what it feels like. Complete with the brief feeling of satisfaction, followed by ennui, followed by getting bored and trying to make it happen again.

This comic is a reference to the video game Tetris, in which you use different shaped pieces to fill in lines to score points.  The more lines you fill at a time results in more points.

In this comic, Heaven is when you get the perfect piece in Tetris that fills out all the empty space you have on the board.

In the image text, ennui means a feeling of utter weariness and discontent resulting from satiety or lack of interest.

I love Tetris.

UPDATE: As Mr. I and Phoenixx have pointed out in the comic, this is a direct opposite of the xkcd "Hell" Tetris comic.

This comic is about 10 images so that it can present the 3D effects, so head over to xkcd if you have not already to check out the comic with the 3d effects. (UPDATE: I have placed a screenshot above.)

Image text: I'm only willing to visit placid lakes, salt flats, and painting exhibits until the world's 3D technology improves.

This comic is probably a reference to the new Nintendo 3DS handheld video game system that has a 3D effect if you put your head in the right place for the handheld device.  Also, it is a reference to the proliferation of 3D movies.  The 3D movies and 3D games make your eyes work harder which can cause headaches in some.

In this comic, Cueball is using the excuse that 3D gives him a headache to get out of going outside, where obviously, everything is in 3D.  Instead he stays inside and looks at his 2D computer monitor.  In the image text, he says he will only go to places with little 3D motion.

On a side note: Megan is wearing her helmet and practicing safe bike riding.  Way to go Megan!

UPDATE: Thanks commenters - because today is April 1st, all of the xkcd comics are in 3D, so go back and check them out.  Which one is your favorite in 3D?

Image text: Wait, that second one is a woman?  ... wait, if that bothers me, then why doesn't ... man, this game is no fun anymore.

This one is not very deep.  FPS is "First Person Shooter", which is a type of video game (like Halo or Duke Nukem) which you are looking at the world from the first person perspective of the character.  Cueball mods the game which is short for "modify".

When Cueball uses this modification, it makes the game more sad because you are presented with facts about the characters you are killing in the game.

Image text: I heard the general anesthesia drugs can cause amnesia, so when I woke up mid-extraction I started taking notes on my hand so I'd remember things later. I managed 'AWAKE BUT EVERYTHING OK' before the dental assistant managed to find and confiscate all my pens.

In this comic, Cueball decides it is finally time to play the game Minecraft (which is quite addicting) because he is getting his wisdom teeth out.  Minecraft describes itself on its website as: "a game about placing blocks to build anything you can imagine. At night monsters come out, make sure to build a shelter before that happens."  In the fourth frame, we see that instead of building anything, Cueball has flattened the continent out.  I'm not sure what the block item in the lower right hand corner of the 4th frame is because I haven't played Minecraft.  Anyone have any ideas?

Cueball makes a strange choice to flatten the continent because of all the painkiller drugs he is on after the wisdom teeth extraction.  In the image text, because Cueball fears amnesia and memory loss from the anesthesia drugs, he writes information on his hand similar to the way the protagonist does in the movie Memento.

Image text: I learned from Achewood that since this poem is in ballad meter, it can be sung to the tune of Gilligan's Island.  Since then, try as I might, I haven't ONCE been able to read it normally.

This is a quote from the first three lines of the Emily Dickinson's poem "Because I Could Not Stop For Death".  In the second frame, what seems to be Emily Dickinson is using the "Y" button from Grand Theft Auto to "carjack" Death from its carriage.

Achewood referenced in the image text is another webcomic.

Image Text: I understand you and your team worked hard on this, but when we said to make it more realistic, we meant the graphics.

In case you’ve been living under a rock your entire life, Frogger is a classic video game in which you, the frog, are trying to cross a freeway (or a swamp). Your crossing is fraught with danger, so you’ve got to dodge traffic in order to make it across safely. It’s a simple game, and doesn’t deal with the real world consequences of stepping out in front of a truck, as today’s xkcd does.

When the comic starts, everything’s fine. There’s a frog on the side of the freeway, and he’s not bothering anybody. When he hops out to make his crossing, however, the driver of the semi swerves to avoid him, causing the sedan to his right (more on that in a moment) to slam into his cab, causing a pretty severe traffic accident. The frog then retreats back to the side of the freeway, though whether or not he’s fleeing carnage or a guilty conscience is up for debate.

Now then, concerning the truck driver. There’s a large grassy area off to his left, and yet he chooses to swerve to his right, into traffic. Given that we can see the freeway at a resolution fine enough to make out lines on the road and that the frog seemed to have no barrier to hop onto the freeway, we can presume there’s no guard rail preventing the truck driver from swerving left. Even if there was, it would be hard to imagine a scenario in which this truck driver is risking more by going through a guard rail than he is by swerving into traffic. The most plausible explanation is that the grey car was in his blind spot. Our truck driver is in this way redeemed, for rather than making an illogical choice to swerve into traffic when he didn’t need to, he’s made a logical choice to keep his truck on the road by merging into what he thinks is an empty lane. This way, he minimizes damage to his truck and any interruption to traffic flow. Of course, he’s miscalculated, and carnage ensues.

…or does it? The image text adds another layer to the reality here, suggesting that what we’ve been watching isn’t real, but a hyper realistic Frogger game being presented for evaluation. Apparently, the memo to make it “more realistic” was misinterpreted. Konami had wanted better graphics, not a more real simulation of what would happen if a frog jumped out in front of a truck. Of course, that’s not even a real Konami- it’s a fake Konami that exists in the xkcd universe, which is of course a series of scenarios imagined in Randall Munroe’s mind. And even Randall Munroe might not exist as more than a mental illusion, produced by some sort of coordinated data parallax put on the web, but if THAT was the case then he’d be-

You know what? I’m gonna go gargle with Thorazine and call it a night.

Image text: All those GTA marathons during the pregnancy were a bad idea.

This is comic that is a parody of all the studies and news stories about the effect of video games on children.  If they play too many violent video games, do they act like the video games in real life?  Most of the news stories are based on one case or anecdotal evidence.  This comic takes this to the next level and imagines what effects video games have on an unborn baby.

My only question is this: how the heck did the gun get in there?

Image text: There's nothing hotter than porn dubbed over with a poorly-mic'd teenager's voice explaining each step in a droning monotone. 'okay, we're almost at the spawn point ... separate the labia, but watch out, there are more inside them ..."

This comic is a pun on walkthrough videos for World of Warcraft instances and bosses and game of a similar ilk.  Videos will be posted online showing how to beat a particular part of the game.  As the image text says these walkthroughs are always done by a teenager and are almost impossible to listen to.

In the case of the comic, the walkthrough video that was watched was what is known as a "speed run" in which the players in the walkthrough try to finish the boss, instance or whatever as fast as possible.  So, as you can see, the joke is that the person incorrectly watched a speed run sex walkthrough video, so the sexual encounter on his date was a "speed run".  If you don't get the joke there... come back when you are older.

In the image text, the word spawn point is used in the gaming realm to mean the place where new enemies burst forth.  In the image text, it is used as a pun.