Batman: Arkham City aka Batssassin's Creed meets Metroidvania

Batman: Arkham City had quite an act to follow. Rocksteady's Arkham Asylum took everyone by surprise, offering a solid action-platforming-brawler with tons of well-implemented fanservice that paid tribute to an age old franchise. And all of this from a developer with only one other little known title under its belt. Arkham Asylum was the ultimate sleeper hit.