5. Realism
So far, almost everything in the Arkham series seems possible. With the exception of Killer Croc, Soloman Grundy and Ra's Al Ghul, every villain seems realistic even though they obviously come from a land of fiction. Batman doesn't have any super powers, which is why we can relate to him. Batman can be anyone. Well, anyone with billions of dollars and is at peak physical ability. Everything about the games has seemed possible and that is why we can feel immersed in the games, movies, and comics. If the Justice League was brought in, the gamers would feel a loss of realism. The design of the Asylum was filled with detail ad felt amazingly real, it was the same with the City. Now, imagine if you were walking down crime ally and suddenly saw Green Lantern flying overhead. That would definitely draw your attention out of the dirty, gritty feeling of the game. Batman's world is as dark as the cowl he wears, the Justice League would be a flash of light that sticks out.