As far as PS3 goes, you absolutely cannot go wrong with Oblivion. I've gotten easily 200+ hours of game time out of that bad boy. Get the GOTY edition too, because Hot damn! Shivering Isles is awesome!
Other PS3 games to go for are Red Dead Redemption. It's got a great story, great gameplay and an amazingly sizable multiplayer, or Just Cause 2, since it's completely batshit insane and you will never have more fun. Plus if you have buddies, Tekken 6 is always fun.
As for anything else, the only other game I can think of that'll get you a good amount of time is Pokemon Heart Gold/Soul Silver, if you're prepared to buy a second-hand DS, that is.
I've just beaten the Elite Four today and I've racked up about 50 hours of play, plus I have the pokedex to fill and all of the Kanto region to explore and pokemon gyms to beat, not to mention legendaries to catch, Mt. Silver to explore and Red to beat. so yeah, another 100+ hours gone.