So I'm turning into a consolefag now, with a PS2 and a modded Wii currently gracing my TV. I've been tossing up between getting a PS3 or Xbox 360 for a while now, and finally settled on the 360 for its excellent media playback -- DivX/XviD support? Shit yes! -- and online capabilities. I understand from the gamertags that there's a few 360 fags around here.

The version I've ordered is the Forza 2 bundle, which I'm pretty sure I'll thoroughly enjoy (I like my racing sims). There are a few other games I plan on getting which I've heard are excellent (Assassin's Creed and Mass Effect). I may also get Halo 3, though I'm not a huge fan of the series.
What other games should I be getting while I'm at it? I'll be wanting a bit of online play, since I've got plenty of stuff on the Wii and already plan on getting the two aforementioned single player games.
Also, I've noticed a lot of games list 720p, 1080i, etc as supported resolutions, but what about if I want to hook em up to an older CRT TV? Do they still support 480i/576i output? I'll most likely use a VGA monitor, but I've got a LG flat CRT with component inputs that only supports 480i/576i, I just want to know if I've got that option.