ok, a quick summation on why this game really IS all that (Aka best platformer and most influential game in 11 years).
Mario 64 took a genre we all knew and loved and transformed it into 3D. We might say now "Well, no duh.. it really isn't that hard of a concept" but for those who remember 1st, 2nd and even 3rd generation 3D platformers in late 95 to late 96 (jumping flash and crash being the most prominent examples) it wasn't quite as easy as one would think it was. Nevertheless, Mario 64 came along and showed everyone how to do it, and made it look easy in the process.
Flash forward 11 years to Super Mario Galaxy. So why is it so great exactly? Easy really.. after Mario 64 showed everyone how to do a 3D platformer, everyone simply copied it. They added fetch quests on, obsessive collecting marathons to tally up achievements, and really just copied everything that made Mario 64 great and changed it just enough to be able to say they made a new game. In many cases this worked just fine (mostly by Rare and later Naughty Dog). So what does Mario Galaxy bring to the table that the others supposedly missed? It is the first platformer that says "Why do we have to be limited to what was done in Mario 64? Why do we have to copy the same 11 year old formula to make a 3D platformer?"
And boy does it fucking succeed. As you hop from planet to planet, utilize one of a half dozen different ability suits, and experience visual, gravity, and logical puzzles that make your head spin, it instantly becomes apparent that up til now, we really HAVE been playing the same game for 11 years. People cite that platformers have died and can't sell more than an average number of copies anymore. I hope, no I pray, that Mario breaks sales records galore. Not because it's Nintendo or because it's a game so good it deserves the sales (which both are true). No, I hope it gets monster sales for the same reason Final Fantasy VII did, and GTA3 did, and Halo did, and Pokemon did. I hope it gets monster sales because it shows us that every limit we thought a certain type of game had are just silly, and that all it takes is the right developer and right group of people to open up a whole new world of gaming to us.
Mario Galaxy is without hesitation my pick for game of the year. Above Rock Band (yes, really). Above Guitar Hero III. Above Bioshock. Above Metroid Prime. Above everything. They are all great games and every bit worthy of consideration for GOTY, but the bottom line is that none of those games, nor any other, will have done for gaming this year what Mario Galaxy will do for gaming. Mario has literally REDEFINED an entire genre of gaming in one. single. fell. swoop. And if that wasn't enough, the game is just pure fun to play. As your hopping from planet to planet to planet in a single galaxy and finding new jump paths, new secrets, and new worlds, even the most cynical "mature" gamer out there will have a smile on their face the entire time they're doing it.