Opening with one of the most unexpectedly fantastic games of all time, nobody expected relative newcomers Rocksteady to deliver (who only had FPS Urban Chaos: Riot Response to their name), but in taking a wayward ball tossed their way by Warner Bros., they promptly scored a monolithic touchdown.
Though sequels Arkham City, Origins and Knight went off in a purely open-world direction, this original entry has the best balance of storytelling, atmosphere, progression and most importantly, rhythmic face-smashing combat. Dropping the Joker off and seeing Batman tower above him was an image worth building a franchise on, and that was before you got into the almost Metroidvania-esque feel of unlocking various new items and gadgets, to further explore the titular asylum itself.
No game had ever embodied a superhero quite like this, and no game ever will again. Arkham Asylum represents an underdog studio putting in the performance of their career, the result being a creation of pure passion and purpose, executed to perfection.