Rocksteady did absolutely everything right in Batman: Arkham City. This includes the stellar sound design; punching thugs makes a satisfying thud, bones make an earth-shattering crack, and even Batman's cape itself has a cast of sounds. John Roesch was the Foley Artist that made it all happen in Arkham City. He also made it happen for The Dark Knight, The Matrix, Inception, and many other huge projects. Basically, he knows his sh*t.
This video shows off how Roesch made the effects. For example, to make the sound when punching Mr. Freeze, Roesch put a snowboarding boot inside a motorcycle helmet and hit with a hammer. This is exactly why I wanted to be a sound engineer at one point. Oh, there's also some stuff about recording gun sounds, but that's a snooze fest. Hitting things with hammers is always more thrilling.
By the way, if you haven't picked up Arkham City yet, you can the Game of the Year Edition releases on May 29th. That's my birthday, and if you don't play Arkham City it'll make me sad on my birthday. No one wants that.