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.
Retail (Tuesday) • Dead Island: Riptide • Dragon's Dogma: Dark Arisen • Star Trek XBLA (Wednesday) • Poker Night at the Inventory 2 (800 pts) Gold Member Deals of the Week (Tuesday) • Peggle, Peggle Nights, Plants vs.