I haven't actually played this one yet, so instead I'll paraphrase what Jaison has told me about it. This game is at least as good as Arkham Asylum, which already makes it better than every other Batman game out there. The open-world structure doesn't add much to the experience, and in some ways it actually bogs down the main story.
The side-quests are entertaining in their own right though, and finding the Riddler's clues is a fun distraction. The boss fights have been improved, and while still not perfect they are leagues ahead of the crap in Arkham Asylum. The Catwoman missions are a good way to mix things up, and aren't that sexist after all. This is certainly the best Batman game, and probably one of the best games overall this year.