The first time I saw it at the theaters, I thought it was in my top 3 favorite films of all time. Of course, this was just hype and excitement after seeing it for the first time.
Upon repeated viewings, it's easy to pick out a lot of flaws in the story and for that reason, I see "The Dark Knight" as a very good film, but not the masterpiece some or claiming it to be.
I really enjoyed the movie, but to me, the main appeal is Ledger. He's just incredible. I try to picture the movie without him and when I do, I realize it wouldn't have been a good movie without him.
By the way, "Batman Begins" is superior in my opinion (and in my top 5) and I can watch that over and over again, but I can't do the same for "Dark Knight." Too many little things in "Knight" just drop the score for me...