Well, it's completely different.
We've never seen a superhero have to grapple with the idea that his heroic choices are actually PRODUCING BAD not GOOD. And we've never had a villian that'd exploit that to his benefit.
Batman Forever sees Bruce put down the cowl because he's obtaining closure over his parent's death.
This sees Batman having to box up his vengence and rage for the sake of the people in Gotham. Missing the point however that by giving in he's doing exactly what Joker wants.
This whole idea of believing in things, in Batman or Harvey Dent, stems from the idea that terror is much more believable because we feel it. Hope is a much vaguer emotion.
Batman is being forced to put down his cape and cowl. Not choosing to. Gotham is spiralling out of his control. The wannabes are bad, the bad are worse, and the worse are becoming Jokers. It's a compelling point that has to give Bruce pause, especially when the Comissioner himself is killed..."People are dying..."
I just love the fact that it's Alfred, the one who was afraid Batman would consume Bruce, that says, "You need to endure it, toughen up, and embrace the beast inside of you because now more than ever Gotham needs it."
This is a much, much different slant on a superhero tale than we've ever seen cinematically. I can't recall one instance where the hero is FORCED to quit under compulsing from the villian driving the city into the ground.
See, now, when the hero re-decides to be the hero, it's not like Superman or Spider-Man where it was like' Yeah, they realized the error of their ways and are back!" And that was a great feeling. Now imagine when it's "Yes! He just said **** you to everyone who doubted him and is going to kick some ass." It's a much more agressive and war-like stance. If this is where they go, I love it. A war-like Batman. That's what we need. A Batman that accepts that they'll be casualities but ploughs on because the principle of fighting is more important than the principle of winning.
Also, what's interesting, is that Joker is turned to by the mob because of Batman. Probably for this very reason: turn Gotham into a hellhole for Batman and make the people hate him. But I'm fairly certain taht Nolan's Joker is no puppet and quickly dispatches the mob as well, aiming for complete and utter anarchy.
I mean, look at it:
You have chaos on the streets. A-listers being killed. The Comissioner being killed. The Mayor killed or almost killed. A hospital blown up. A massive bank destroyed. Semi-trucks flipping up in the streets. Gotham has gone to hell. They blow up a mall. Joker gets cops to flip out. He possibly kills Rachel Dawes. Harvey Dent gets disfigured. Fundraisers being crashed. Wannabes taken hostage. News stations being attacked. Reporters being killed. All this is going on due to the arrival of the Joker....
Batman's only option is to declare war, a principled war, but a war nonetheless.