@Zekhariah: You're completely right. The real winner is Call of Duty: Modern Warfare. And there are a ton of different metrics in which to judge a game.
However, a pertinent way to judge a Game of the Generation could be influence on future games. In which case, Gears of War is a strong contender. It's influenced a great number of games this generation, perhaps more than any other.
I was more just putting forward the idea, so that the Giantbomb crew could see whether the community reacts positively to the idea. Save them a little trouble.
However, I'd love it if people discuss their opinions. My personal choice would be Super Mario Galaxy, for being the purest form of unpretentious, honest video game adventuring yet. Exploring worlds, testing your skills in wonderful lands. It's a video game's video game.