In my opinion, "The Dark Knight" is not all that grand or deep of a film. Good actors, and an outstanding performance from Heath Ledger, and a basic story that seems to be quite earnest in how it's presenting Batman and exploring the ethics of his actions, but I just don't see it as all that sophisticated a work of cinema. In many ways, its execution is rather like the new "Star Trek" picture: a slick entertainment with underwhelming production design, juvenile action scenes and a dearth of imagination. Funnily enough, both also try to be too "real world": TDK with its totally undisguised Chicago and gritty (yet still sanitized) feel; ST with its creaking shuttles, water pipes and valves, casual references to bestiality and slang words like "man" in a bar setting, etc. Neither is shy about stereotyping people, either (in TDK, the Chechen drug dealer; in ST, skinheads as antagonists -> typical Hollywood misdemeanours). Oh, and they both have main characters on a bike -- a cliché wrapped in a contrivance wrapped in a platitude, and the epitome of trying too hard by not really trying at all.
