I have no idea about Resistance 2, I apologise.
Fallout 3 is a HUGE game. The Wasteland is so expansive and there's side quests everywhere. Just because you finished the main story doesn't mean your finished by a long shot. I'm not sure whether the DLC is available for PS3 users at the moment.
LittleBigPlanet is also amazing, and also very expansive. A lot of joy comes from creating and sharing levels though, so unless you have online and friends with the game it's a bit pointless.