Hmmm... Nope can't think of much. The only games I own on PS3, I also own on Xbox 360 and I must say the 360 versions have always been better at this point.
I don't know of many multi-player action/rpg's out for the PS3, but one thing you can try is the downloadable game Pixel Junk Monstors Tower Defense game. It is really addicting and 2 players can play coop.