Why Some PS3 Games Look Bad When Running in HD?

Hi ppl im Having probs with my PS3 and the monitor,

im using my Samguns SyncMaster T240 to play my PS3 games on my room but it looks like the games lack of AA or something like this is this normal in 720p games? cause in KZ2 GT5P, and other 1080p games i can't see this happening yesterday i was playing Uncharted 1 and it looks like it lacks of AA am i suppose to do something in the settings?

Cause like this some games like resistance 2, uncharted 1, infamous looks a bit better on SDTVs...

Are you stretching the image of the 720p games? I have the Samsung SyncMaster 2433 which I use solely for my computer, but older games that don't have 1080p resolution can either be stretched or show black bars. It would obviously look much better if it weren't stretched.