You be crazy to get a PS3 right now. Sorry, Sony fans. As much as the Sony is the "better piece of hardware" it also turns out that it's a pain in the butt to program, and the code you write to program it is not very portable. Soooo, PS3's game selection leaves a lot to be desired currently.
XBox360 games that rock: Dead Rising. Oblivion. Halo 3. Overlord. Bioshock. Viva Pinata is a lot of fun, not that anyone bought it. For god's sake, Bioshock. Mass Effect any day now. GTA4 at some point. If you like casual games, you can get PacMan HD, Carcassone, and soon Talisman on the Arcade. Geometry Wars is great of course. There's enough on the Arcade alone to keep you occupied for a couple of months.
PS3 games: uh... Oblivion... (chirp) (chirp)... I hear Heavenly Sword is good for a whole 5 hours of play... (chirp) (chirp)... Eye of Judgement? I hear Flow is original, and you get to hang out in a virtual house with other people who wish they had some games to play. PS3 may some day ascend to a throne of powerhouse platform, but so far everything that has come out for it has either (a) come out for the XBox360 first or (b) has sucked.
PC is of course good, but it's becoming the second release point for a lot of games (especially RPGs). It does still have NWN2, but maybe that isn't that great of a selling point. If you like strategy games, then PC still has quite an edge there... At least until Civilization Revolution comes out. Who knows whether that experiment is going to work though.