When it comes right down to it, the superhero as a concept is a troublesome being. Useful when s/he's under control, a benevolent para-law enforcement agent, exercising great responsibility over their great power. But in the end, we're still dealing with a group of people outside the law because there are no laws which can touch them, and precisely there to combat those villains the same laws can't touch either. Superman, for instance, is tolerated because everyone knows he's a boy scout who will do no wrong. But isn't it taking a lot on faith to assume that this godlike being isn't going to figure out that we're all inferior?
The Dark Knight takes a lot on faith as well, but the fact that the film is about the murky relationship between the public good (as dictated by those in the know) and ethics and vigilantism and chaos says a lot. Batman is still the hero, but it is acknowledged that he may be the sort of hero no one can own up to, that may well be morally reprehensible, that may in fact be contributing to the lawless streets of Gotham City. As in the Arkham Asylum graphic novel and the animated series episode which put Batman on trial for creating Arkham's denizens, the film is aware that there's a problem here, even as it shores up Batman's continued necessity in a diseased world.
While he'd most likely disown both, I can't help but observe that Nietzsche inspired both Superman and Hitler.
For a summer action movie, The Dark Knight is pretty self-aware and addresses some tough issues. It's basically action (which it is completely worth taking advantage of the IMAX experience to enjoy) with archetypes, and while it would be nice to have something which could accomplish that with actual characters, I think that's asking a lot of a corporate property summer blockbuster like this. Which is to say, this movie succeeds far more than I felt I had any right to expect from a franchise, and that made swallowing some of its inadequacies a lot easier. There were the requisite technological absurdities (an expansion of the “enhance!” trope you might be familiar with from any number of cop shows), a silly Batman voice, and some far-fetched physical feats. But then there was also (do I even have to say it?) Heath Ledger's Joker.
Praise has already been heaped, and it's well-deserved. This was not a casting decision I'd ever have expected, and Ledger had pleaded his case to director/co-writer Christopher Nolan before the script was even written. This is the scariest Joker I have ever seen (though the effect was not as acute on second viewing) and while it's certainly possible to prefer the more lighthearted incarnations (Mark Hamill's in the Animated Series should be classic) this reinterpretation is an achievement, taking the character to a place that is not only unique but integral to the film. This Joker and Batman are two sides of the same coin, which makes the inclusion of the Harvey Dent plotline, who is both sides of the coin at once, especially relevant. Thematically, the nearly unbelievable self-awareness of the Joker (and his lack of an origin story) culminate in his abuse of Dent.
The Joker's admission that he is an archetype, an agent of chaos, along with Bruce Wayne's inability to define just what the Batman is, leaves the film with an ambiguity that keeps both the legend of the superhero and his troubling ethical legacy intact in a way that, I believe, finally serves the material well. Complaints about its “relentless sadism” and moral deficits miss the point; if you're disturbed by a Batman which admits there's something wrong here, you should probably stick with the fully deputized, establishment, daylight Batman and Robin of the Adam West series. Superheroes are a fantasy which, when translated into the real world, starts to look a lot like fascism.
This movie is not perfect, nor did it change my life. But far more than its predecessor, Batman Begins, it addresses the inherent issues that have always plagued this character, and for that I am overjoyed.