I currently own/ have owned
PDZ LE (picked up at launch)
PGR3 (day after launch)
Condemned (day after launch)
Kameo (1 week after launch)
THAW (end of december)
DOA4 (release day)
Amped 3 (last week) - got used in trade for THAW
Ridge Racer 6 (yesterday) - got used for $40
COD2 (current in the mail coming to me) - got used for $45
PGR3, THAW, Kameo, and DOA4 I've played through there initial runs
I'm currently playing Amped 3 and will work on my other games once that is done.
For the rest of the year:
Games that our out now:
Quake 4, NFS Most Wanted, Gun, and King Kong - I'll buy these used, trade them for games I have or borrow them from friends once I start to get bored or 100% the games I have now.
Full Auto - I'll wait to buy this used, it seems like a pretty shallow game, but if it's got 4 player split screen it'd be decent for parties where most people playing don't have any experience with the game.
Fight Night Round 3 - probably buy used or in trade, play through it, trade it for something else
Oblivion - If the limited edition comes in a metal box, I'll be buying the Limited Edition on release day simply because it comes in a metal box, if it DOESN'T come in a metal box I might not pick it up at all (I bought PDZ, Halo 2, Doom 3, and True Crimes NY for the same reasons). I'm just not a fan of western style RPGs, but I am a fan of metal boxes.
Splinter Cell: Double Agent -

Sam Fisher is my Hero... now if only Chaos Theory would play on my 360 so I can finish it before this one comes out.
Burnout Revenge - Probably pickup used or in trade after it comes out, it will stay in my collection at least until Burnout 5 is on the radar, it's a good game for parties.
Tomb Radar Legends - Definitely picking up on release day... I've been waiting for a TR game with modern graphics and the classic gameplay...
Gears of War - picking up on release day... I'll get the LE version if there is one available.
Prey - picking this up on release day.. game looks DAMN awesome
Too Human - looks interesting, I'll play this one by ear and see what the hype is around release time.
Enchant Arm - I love the Japanese style RPGs, this one looks somewhat interesting. I might pick it up used if it ever comes out stateside.
Down the road:
Halo 3 - whenever it comes (I honestly doubt it will be this year)
Mass Effect - looks interesting even if I don't like that style of RPG
Killer Instinct 3 - Rare better release this, they would be foolish not to, The Xbox NEEDS fighting games BAD (sorry SF2 doesn't count), IMO this would have made a much better launch title then PDZ, not to mention it would have sold better then PDZ in Japan, and given them time to make PDZ the FPS king that everyone really wanted it to be.
Resident Evil 5 - picking this up on release day... RE is one of my favorite series.
Rallysport Challenge 3 - YES... this game will own my LIFE
Honestly though the Xbox has somewhat of an overabundance of FPS and Racing games, and is severely lacking in Fighting Games, and Adventure games. Kameo was awesome but how much longer will it be before we get another decent Adventure game. Same can be said for DOA4... we don't even have any officially announced Fighting games down the road, how sad is that?