Yep, it's Super Mario Galaxy. Here's what Gamespot said when they picked it:

Deciding this year's winner for Game of the Year was probably the single toughest award deliberation that GameSpot's editors have ever had to participate in. Even narrowing our top list of finalists to just 10 games was extremely challenging and very, very, very contentious. Really, any game in our top 10 list would make a fine winner and could be easily supported by some very strong arguments.

Ultimately, it came down to Super Mario Galaxy as our top game because it is (by a narrow margin indeed) the best overall package of polish, gameplay, and presentation for what it is--a traditional but highly evolved platformer. Let's face it, this is a game that Nintendo could easily have phoned in and still sold about a zillion copies. We could've seen a game that took very few risks and more or less replicated the same old stuff we've seen in previous games. We could've seen a game that relied heavily on nostalgia value and trotting out the same old characters and reprised music tracks instead of adding in fresh and exciting new content. Traditionally, every Nintendo console has been christened with a blockbuster Mario adventure, and with every Nintendo console launch, fans everywhere are always ready and waiting to grab their copy simply because the game features their favorite video game plumber.

But that didn't happen. Nintendo didn't take so much as a single step back with Super Mario Galaxy, and instead reinvented Mario's traditional platformer adventures with beautifully designed levels that make unique use of zero-gravity gameplay and clever, enjoyable puzzles. All of the levels are varied and look fantastic, and they even add replay value because the game has a set of collectible stars that you can go back to hunt for, as well as a limited but still enjoyable multiplayer mode. This is a game that plays great and looks fantastic; this is a game that you can recommend to basically anybody who might have any interest in video games--without having to qualify it or apologize for it with "it's great, but."

Again, this was by no means an easy decision to make, but GameSpot's ultimate pick for the top game of 2007 is Super Mario Galaxy. That's no reflection at all on our other nine finalists, all of which are remarkably good games in their own right and all of which are absolutely worth playing. For a year like this, with so many incredible games available to play, the real winners are each and every one of us.

Awesome, huh?