It is one of mine and my brothers favourite games. I have not heard of anyone not liking Batman: Arkham asylum. You probably don't need to play that to play Batman: Arkham city but it could help you get used to the game mechanics (unless they have radically changed them) and it is a very good game, so it couldn't hurt picking it up, since now you can pick it up quite cheap. You really don't have that much to lose.