ok heres your lesson for the day my 360 loving brethren, and this is old news....
old dev kits didnt have the edram and new ati card(some had geforces even), so it was up to the developer if they wanted to use any AA at all, some did, some didnt. Some figured why bother if the final will give it to us.
and not all older 360 pics have aliasing problems. recon 3 didnt for the most part, PGR 3 never did, gears looked good, while games like need for speed, test drive and others DID have aliasing problems.
now that launch is close, and the kits are close to final hardware, expect to see cleaner pics. If I of all people am not concerned about jaggies in some pics, noone should be.