8. Tetris
The fact that the game has been reproduced a few hundred times over with different shapes, different colours and different add-ons (such as increasing speeds, bonus points, etc.) is a testimony to the games' greatness. There's no game that has been around for so long and is still played by people with undying affection and vigour. In fact, the obsession has stretched so far that scientists have conducted researches on how prolonged Tetris activity (not just a game, mind you; it's an activity) can lead to more efficient brain functioning. Tetris has been the subject of disputes over the ownership of rights over the game. People have used computers to test various permutations that could occur in the game. It's become an obsession. What's beautiful is the simplicity of the game. Much like a Rubik's cube where there is a singular, known purpose that has to be accomplished, Tetris is all about placing falling blocks into a correct sequence. And though the game was first know to have been played 1984, the fact that cellular phones and iPods still carry a version of it really goes to show just how much it means to the world.