Honestly, that's what Modern Warfare 2 looks like (on my displays). None of the games you listed are overly pretty, though Borderlands' cell-shading graphics help out a little bit to my eyes.
Remember, the 360 isn't making these games 1080p. As others have said, most games are developed well below that resolution (600p, 640p, etc). What the 360 does to any game is essentially do what a up-converting DVD player does: up-converts the source to the resolution you specify.
Just because you select 1080p in the system settings doesn't mean that games are 1080p. I wish that were the case, but unfortunately it isn't.
PSN ID/XBOX Live! Gamertag: BiffCo