Hmm, I kinda disagree with you there. Strong contender for GOTY but it's not Mario 64. Game of the decade would probably be something like Deus Ex or Grand Theft Auto III. Mario Galaxy just doesn't have that dazzling entrance on the scene that Mario 64 did, where it really did send shockwaves through the gaming industry. A muted reception compared to its illustrious predecessor, if you will. Other games since Mario 64 has resonated far more with gamers in general, including the two I've mentioned earlier.
We'll have to agree to disagree
I've never seen a game get such a positive reaction from gamers - even Mario 64, which is probably my favourite game. Deus Ex was very good (I prefered SS2), but certainly doesn't have the widespread appeal of Galaxy or 1/10th of the polish and design quality. Let's face it, even for its time, the combat in Deus Ex was ropey at best.
I agree that Galaxy hasn't matched Mario 64's entrance, but then again, how could it? We've had 3D and analogue for donkey's years now. If anything, this makes Galaxy's massively positive reaction even more worthy of praise. We're not being wowed by the inclusion of a 3rd dimension and all the new gameplay possibilities that comes with it, but because in terms of creativity and imagination Galaxy is in a class of one.