They sincerely haven't realized how much milk they can squeeze out of the PS3...
I mean... it's not all about graphics... for god's sake! Just do something about average... like at Half-Life 2 level, but with physics 10 times as intense, and everything is shootable/breakable/killable/etc... and you'll suddenly find yourself in a completely different experience. It's not impossible... and it's not a lot of work either. It's just that a lot of developers just run after the trends...
Edit: but after that PS3 rant, I bet quite a few should realize that: we won't get anything original or new... as long as all we see are visual enhancements. Sony brought about quite a revolution. They just don't even know how to do it themselves... or maybe they did, but they are saving it as a secret weapon.