Not sure if you are into the Star Ocean series, but I will recommend Star Ocean: The Last Hope International. A lot of people didn't like it very much (the story is mediocre and the pacing isn't very good in some spots, i.e. very long cut scene then very long dungeon) but I can't get enough of it.
It's a good battle system and a lot of collectibles (literally like 500 hours of gameplay if you try to do everything and get all the PSN trophies and stuff).
But like I said...might want to try the demo...its definitely not for everyone.
It's not an exclusive, but Vanquish is a favorite of mine. If you like hailstorms of bullets, big robots exploding, and great visuals then it's the game for you. CGR Mark rather likes it: http://www.youtube.com/watch?v=JAN2-OZ3it4
Also, the Ratchet and Clank Future games on the PS3 are rather good. I've only ever played Tools of Destruction, but the other two get good ratings on Metacritic, so they're probably very good.
As for RPG games, I can't really think of any that haven't already been listed above. If you're not interested in just exclusives, there's always Fallout 3, Fallout: New Vegas, Borderlands, and Oblivion if you haven't played them already.
another update, demon souls was pretty meh from what little I played (only about an hour) but I popped 3d dot heroes in and just can't stop playing it, its stupidly fun and is really what I think I was looking for, I might even play all the way through thiis one!
Las calles no son basurero, POR FAVOR TIREN LA BASURA EN SU LUGAR !!!!
MY boss pretty much told me the same thing about demon souls, it just feels like a kings field rip off with pretty graphics, the combat doesn't seem inspried at all....I'll give it another try this weekend since everyone seems to hold it in high regards, maybe i'm missing something blatantly obvious?
You'll find Demon's Souls on favorite PS3 games lists for good reason. The combat is flawless and is what makes Demon's Souls. Having excellent graphics doesn't hurt either. I'm a fan of almost all FromSoftware games and Demon's Souls is one of their best, arguably the best, but that depends on who you talk to.
Even though the single player game is amazing, nothing is as fun as playing as or fighting against a Black Phantom(PvP battle.)
Dark Souls is going to be amazing and 360 only owners will finally get to try.