VideoGame A truly cinematic experience.
One of the most interesting conversations in the community of videogame philosophers is the idea of emergent narrative - the story and Emotional Torque that isn't in the text or the cutscenes, but, like the idea that a queen is worth nine pawns, is created by the way the game plays.
Valve gets this. And when they created Left 4 Dead, they did it right.
This game trains you to be a zombie movie protagonist - you shoot for the head, you never split up, and No One Gets Left Behind unless they're dead. The game mechanics support the narrative of the zombie movie - the enforced darkness when the Witch is near; the fading of the light as you lie bleeding on the ground, desperately firing your pistol at the zombies swarming around you; the agonizing slowness of your pace when you've taken major damage; and, of course, the terror of the lone survivor, sprinting towards safety knowing that every monster in the world closes in.
It can be played one-player or over the Internet, but I recommend holding a LAN party or meeting friends at an internet cafe, if at all possible. After all, your only hope of survival depends on your three comrades, and if you want to avoid the natural limitations of computer-controlled characters (although that can be mitigated to an extent via the built-in voice-command macros), it's best to have partners for whom the GIFT doesn't apply.
VideoGame The modern equivalent of arcade action
Left 4 Dead can be said to be many things, and Robin Zimm's review specifically points out how expertly the game takes the narrative style of zombie movies and turns it into actual gameplay rather than mere cutscenes. However, having no such familiarity with zombie movies, I'm going to focus on a different aspect of this game.
Left 4 Dead is the evolution of arcade design, whether its developers realize it or not.
Video arcade games were known for having a certain design philosophy. They allowed multiple players to join at any time, they had a simple gameplay concept that was easy to understand and quick to learn without the use of any tutorials, and they often rewarded you with repeated death to make you try again. In the arcade, all these elements were designed to get you to pay money. Drop-in multiplayer was done since enabling players to join by the simple insertion of a coin meant players would be more likely to join a game in progress, paying to do so. Simple-to-learn gameplay meant anyone could pick it up and players wouldn't feel intimidated. And the challenge was of course to get players paying more money to keep playing.
But all these elements serve a different purpose here in Left 4 Dead. The game is a first-person shooter with a very simple goal: reach the end of the level, and fight off zombies that try to make that goal difficult. Additional depth comes in the form of strategies like throwing a beeping pipe bomb to lure zombies away from you, using molotovs to set them on fire, as well as elements of cooperation, such as pulling a downed player to their feet. This depth is conveyed to the player through helpful onscreen messages, eliminating any need for a tutorial, ensuring they jump into the game and quickly learn how to play, making it less intimidating to newcomers. The challenge is variable and selectable, but many players enjoy higher skill levels because they don't make survival an automatic certainty.
This use of the right kind of arcade-like elements is something more games could probably use. While Left 4 Dead may have moved on as players got bored of it, the design mentality behind the game helped it become a million-seller, and something can be learned from that.