I can only refer to the games that are also on xbox 360.
As mentioned Bioshock 1 & 2 were great if you like horror survival games, Fallout 3 & New Vegas are just friggin great epic RPG/shooter crossovers (mainly RPG) & Borderlands is all kinds of fun. The best game across platforms has got to be Red Dead Redemption though.
For something a little different and family appropriate, Ghostbusters is pretty great too. I bet you could probably get it pretty cheap.
PS3 Retail Releases (Tuesday) None PSN Store Update (Tuesday) PS3 Full Games - Bioshock ($19.99) - Call Of Duty: Modern Warfare 3 ($59.99) - The House Of The Dead: Overkill Extended Cut ($19.99) PSN Games - Zen Pinball 2 ($0.00)