The Batman was the only one the three most iconic comic book superheroes (the others being Superman and Spider-Man) who had never really been done correctly on the big screen. Bats was a generic bruiser in a forgettable (and largely forgotten) serial in the 1940's, dragged through the campy mud of the 60's TV series, and seemingly wrecked beyond repair by a series of progressively-more-awful movies from 1989-1997. Anybody who still thinks the Tim Burton version in '89 was any good should go back and try to watch it again today. You'll notice very quickly that stripped of the hype it is a remarkably bad movie, made by a director whose most salient trait is utter contempt for his audience.
(I would be remiss if I didn't stop here to note an exception, the wonderful "Batman: The Animated Series" from the early 1990's, and its producer, Bruce Timm. Check it out on DVD.)
That was, of course, before Christopher Nolin's 2005 "Batman Begins," a well-intentioned reboot of the Batman origin story. "Begins" was an uneven affair, boasting great performances from a top-rate cast, as well as a plot that didn't make much sense and dialogue so cornball it probably made George Lucas cringe. But the story's foundation was solid, the art and direction top-notch, and the creators were obviously intent on making a serious movie around a character all too prone to unintentional comedy.
I'm happy to report that "The Dark Knight" is head and shoulders better than "Batman Begins." The script is much stronger (although not without flaws), the story much more believable, and the production as a whole has both the grit and the sheen of a thoroughly serious production. Much has rightly been made of the late Heath Ledger's riveting performance as The Joker, but Nolin and his brother Jonathan deserve just as much credit for writing the words Ledger hisses with such malicious abandon. It's the smartest character dialogue in a big action movie since the original "Matrix" in 1999.
The look of the movie is close to perfect. Unlike the obviously computer-generated Gotham City of "Batman Begins," this Gotham looks like a real place (which makes sense, as most of the movie was shot in Chicago), and I never had that "Ah, that's a pretty CGI background" feeling that was so prevalent in the first movie. There's also much less dependence on comic-book science. Bruce Wayne's technology, while high, is still grounded in devices the audience both understands and recognizes from their own lives and the world around them.
It's not a flawless movie. Like most big Hollywood flicks these days, "The Dark Knight" runs too long, through a propulsive but convoluted plot, and by the end the audience is more than a bit wrung out. As others have noted, the movie loses momentum after the big set-piece street chase halfway through, and Batman spends too much time in the last 45 minutes battering faceless henchmen. Nolin probably could have cut a good half hour of a Mob-war subplot alone and still had a solidly-constructed story, and a "Batman as 007" sequence set in Hong Kong probably belongs in a different movie altogether.
But in the end, these are quibbles. To the enduring credit of Nolin and his gifted cast and crew, they've managed to produce a superhero movie worthy of the adjective serious, with no ironic modifiers required. "The Dark Knight" is certainly the best superhero movie ever made, and in this case, that is not damnation with faint praise.