Bruce states, very clearly n the first act of Batman Begins that he will be coming back to Gotham for as long as it takes to show the people of Gotham that their city doesn't belong to the criminals and the corrupt. He becomes an elemental symbol to inspire them to want more and do better. I feel like in The Dark Knight we actually see him mostly succeeding. He's taken out the head of the mob in the city, causing organized crime to be in disarray. He forced the police force to clean itself up and become ambitious again. He inspired Harvey Dent who along with Gordon and Batman took out all the money launderers and organized crime in Gotham....but then Joker turns it all on its head, turns Batman's symbol into one of horror and then to cover up Harvey Dent's fall, Batman becomes the monster. This lie to save Dent's image allows Gotham to continue its clean path with some suspect legislation, but it builds its foundations on a lie that when the truth comes out is used by a madman to descend Gotham into more chaos and self-destruction than Bruce could ever imagine in BB. Yes, he saves Gotham from that madman at the end and now Gotham knows the truth about his symbol being one of a heroic nature....but is Gotham's soul saved? Will Batman saving Gotham from Bane's bomb actually inspire the city to do better? Or did he simply accept that he did as well as he could by saving the city from an existential threat and leaves it in their hands to rebuild into a new city? I am not sure if he actually succeeded in the movie.