Depends on what genre you like best.
If you like stupid fun, just messing around killing people, then Prototype is your best bet. I spent more time running around killing random people than doing missions. I would get this over inFamous since Prototype has new game + mode where you keep all your upgrades and can start the story over, where in inFamous you can continue to play when you finish the last mission but there are basically no more baddies to fight... boring.
LBP is fun if you like platformers. I never got into the create your own level thing cause it requires a lot of time to make something of quality. The included campaign is a blast to play through, and the online submitted levels greatly extend the life of the game.
Uncharted 2 is supposed to be amazing but I haven't started it yet.