There is no such thing as replay ability with QW it solely a online game.
I'll be honest I played Crysis on easy at first and finished the game now I am playing it on hard and you have to play the game much more different because the amount of ammo thats at your fingertips doesn't change but the amount of rounds that you use is definitely more. i found myself shooting supports on buildings using the gas cans as bombs much different than the first time. And much more fun. I say Crysis.