Mario Galaxy is truly everything that is fun in videogames, rolled up onto one disc that simply everyone must own.
When Mario 64 invented the proper 3D platforming genre more than 10 years ago, what followed was a river of wannabe clones that didn't quite seem to get the point. Even the sequel to Mario 64, Mario Sunshine, didn't seem to get what made the original platformer so fun in the first place. It took Nintendo over a decade to reïnvent the genre, and with Galaxy it finaly did.
Instead of big, open worlds, in Galaxy the player is confronted with countless of smaller planets. This allows Nintendo to throw small idea after small idea at the player. The result is a game that never bores, it just simply keeps on giving. Where most games would present one good gameplay idea and build from that, it seems that in Galaxy there are tons and tons of ideas that are used for just one or two times, then get thrown away for something else that is at least as fun.
Galaxy is easy to play but hard to truly master, which is what makes any game great. Truly the reason to buy a Nintendo Wii. Platforming has never been this good.