We're all entitled to our opinion. Some think TDK is overrated, some prefer Batman Begins. Some seem to prefer the Burton Batman. I'm sure there's someone out there who prefers the nipple-laced Schumacher version of Batman and Robin.
I don't consider myself an expert on much, but I've spent a long time watching super hero movies--it's sort of an accepted way for adults to read comics, which I probably quit reading too early in life, this is my form of compensation.
My view is that the Dark Knight is borderline genius work. I wouldn't say that about any other super hero movie--I think there are scenes of others that are on that level--the train scene in Spider Man 2 comes to mind.
The Dark Knight has so many components that are easy to ignore--but think back to the first time you saw it. Have you ever seen a bank robbery like that scene--it was utterly original and set the scene for the movie. The scene with Ledger introducing himself to the crime bosses (the pencil trick is disturbing, but you laugh anyway). The scene where Batman interrogates Eric Roberts--brilliantly funny and sensible. The interrogation scene with the Joker in prison--which I think both Nolan and Bale cite as their favorite, is gripping as well. There are little things sprinkled in as well--Ledger applying anti-bacterial cream in the hospital, that round out the fillm.
People argue that Ledger stole the film--okay, what's wrong with that. It was a fabulous performance. It remains remarkable that he won an Oscar--which I think he would have gotten whether he passed away or not. Nolan obviously recognized where Ledger could take the movie and gave him some liberty. Small things, like licking his lips constantly, weren't scripted, they just seemed natural.
Are there flaws?--Batman's voice is silly--and painful (try to impersonate it for a 5 minute conversation-you'll be coughing). But if you think back to when you first saw it, you may remember the incredible craftsmanship and originality of the movie.
Just my $.02.