I think if this was any other GTA game aside from San Andreas then that would probably get my vote but it's not. I just didn't like San Andreas, I didn't like the landscape, I didn't like the story, I didn't like the amount of time it took me to cross the width of the map for a single mission.
Arkham Asylum on the other hand was simply pick up and play brilliance with a cast of famous characters, a pretty damn good combat system, a huge map and a solid story. More than anything else though it could not have done a better job of being a Batman game. As I've said already, the older ones amongst us have been waiting 20 years for a game that truly immerses you in the Batman world and all we've had in that time was a pile of crap, Arkham Asylum was the game we'd been waiting for, and it was glorious.