Here's many great choices and reasons they might be good for you:
Perfect Dark: Zero - Almost everyone will own this game . . it's the new Goldeneye
Oblivion: If youre an RPG fan, and/or enjoyed Morrowind, it's a must have
Saint's Row: Grand Theft Auto CLONE. Might be great, might not be, but I'd wait for crackdown, a more well thought-out game.
Call of Duty 2: I personally love this game, WW-II game that makes you feel like you're in the action. To d/l a PC demo:
http://www.callofduty.com/cod2/demo.htmlCondemned Origins: This is just like a Resident Evil game; unless you play it in the dark with some nice speakers, it'll suck.
Project Gotham Racing 3: Shows off the power of the 360; a typical racing game with amazing enviromental effects.
Need For Speed: Massive car customization, racing type game, graphics are great, but not quite up to PGR3.
DOA4: I don't like fighting games, but if you've played 2 or 3, you'll know exactly what to expect from 4.
Kameo: Most might like it, but I see this more of a Zelda meets Crash Bandicoot game; the music is great in this game.
Quake 4, Tony Hawk A. Wasteland, Madden, NBA, NHL, Top Spin (Tennis game), FIFA, Tiger Woods?
These ones, I think you can make your own judgment about.
Anyways, at launch I'm going for:
Need for Speed: Most Wanted
Call of Duty 2
Perfect Dark: Zero
Elder Scrolls: Oblivion
Good Luck!