Well, it's hard to give an exact number of hours. But typically, to complete the core story of Arkham Asylum without getting too bogged down in extras, you could expect it to take around 10 to 15 hours.
One great 'Batman Arkham Asylum' fanfiction is 'The Dark Knight's Redemption'. It delves deeper into Batman's psyche as he battles his inner demons while trying to escape the asylum. The author does a great job of capturing the dark and gritty atmosphere of the game.
The story in Arkham Asylum often involves Batman trying to stop the chaos within the asylum. The inmates are let loose, and he has to face his rogues' gallery, like the Joker. There are many psychological battles as well as physical ones.
The Arkham Asylum in the graphic novel is highly significant as it serves as a central and dark setting. It's a place where many of Gotham's most deranged criminals are housed. It represents the extreme end of the city's madness and decay, and often acts as a breeding ground for more chaos and villainy.
In this fanfiction, Naruto could be a patient in Arkham Asylum. He has lost his memory and believes he is in some strange version of Konoha. The doctors at the asylum are trying to understand his 'delusions' about ninjas and chakra. Meanwhile, some of the more evil inmates sense his power and try to manipulate him for their own gain.
Overall, the Arkham Asylum game is fairly faithful to the comic. It features familiar characters and settings, but there are some gameplay-driven tweaks and additions to enhance the interactive experience.
One possible plot could be Harry exploring the dark secrets of Arkham Asylum. He might encounter various infamous inmates and try to survive their threats while also uncovering a conspiracy within the asylum's walls.