I don't know. I'm in the minority, but I just wasn't blown away by Galaxy. Great game, sure, but I could name several games of this generation and the last that I think are a little better.
The tricky thing about reviewing Galaxy is that it's so technically well-done. It's beautiful, it controls wonderfully, and the various minigames and suits add a lot of variety to the game. But it just doesn't have the heart and soul of games like Smash Brothers Melee, Shadow of the Colossus, or the original Halo, say. There's virtually nothing in the game that you can point to and say "this should have been done better" (the camera is one such thing), but, somehow, all of the wonderful pieces just don't quite fit together into a wonderful whole.
It's the little touches. One of the best parts of SM64 was that levels changed, often in very significant ways and often for the better, based on your actions elsewhere. The first level of SM64 is great when you first play through it - you see Mario in all of his 3D glory, you scale a mountain, and you wrestle a giant bob-omb. But it gets even better after you get the wing cap. Then you're flying everywhere, and I imagine that I'm not the only person who would start up the game solely to fly around that level. Nowhere in Galaxy do you get that kind of freedom - the flight you do get access to is always very limited. The bee suit isn't in many levels, and it's never just in a level as something fun to play around with - it's always in a level as something you need to get the stars. The game never does something like what SM64 does by throwing the wing cap into the lava level. Even when you do find the red cap very late in Galaxy, you can only use it on the hub.
I suppose my biggest gripe is the general lack of freedom. While the planetoid system is interesting and fun, it would've been nice if some of the levels were as big and open as some of the SM64 levels. While there were some that were as expansive, they tended to be water levels or to have other constraints that stopped you from freely moving around them, and they certainly didn't give you almost unrestricted flight to explore them with. With SM64, I was always poking around in corners or trying to get to places that looked just out of reach. With Galaxy, I only rarely felt the desire to do that, and it tended to be impossible. And that's where I find a lot of the magic in games.
Edit: That's not to say that it's not the best game of the year, which it might well be. There's nothing on the PS3 that I'd put up against it, and, while Mass Effect is also a great game, there are more 'little things' with it and one or two big things. Bioshock and Portal remain strong contenders in my book - Portal moreso.
