Quite frankly, GF2 was awful. I can't tell you how Crackdown is, but GF2 is a game I would not spend more than $5 on. Maybe $10 if I was rich.
GF2 was extremely easy (I didn't die once), had a much shallower feel than the original, etc. An odd aesthetic choice which could be a turn off to some (and would make it difficult for me to play with my gf around): they had TONS of topless girls in practically every building, as if that was the only reason for the game's existence. The campaign is incredibly short. Multiplayer is awful. I hope I've made my hatred for this game clear.