Which Ps3 game should I get?

I currently have the buy 2 get one free at gamestop and I'm trying to narrow down my choices. I know I'm already getting Red Dead Redemption for $35. And my next choice is between Dirt 3 ($48), Sims 3 ($35), Dead Space 2 ($35), or Killzone 3 ($55). Which one do you think I should get and why?