What makes TDK so enduring is how it finishes out in the end. Everything in the movie gets better when you realize what Joker's endgame is and the lesson Batman is going to learn in the end. What Alfred tells Bruce throughout the movie prefaces that EPIC speech about Batman being a "Dark Knight". When I first watched TDK I thought it was a great film, subsequent viewings have made me view it as a masterpiece.
TDKR not only makes that TDK ending much less epic than it is (So, a Dark Knight must endure by....quitting?), it also builds toward an anti-climactic ending.
Wow, Bane is an awesome villain. Look how much he is destroying Gotham. Why is he doing all this?
Oh, because Talia wants him to
Wow, Bruce hasn't been Batman for eight years. I guess we're going to see how hard it is to get back in the game.
Unless he finds a magical brace
Oh my god, Bane is going to take over the city and prevent the government from entering it. I wonder how the citizens will react
They'll conveniently be hiding in their houses for five months until everything is over.
Wow, Batman might actually die in this movie. Unless he fakes his death because.......because......
The movie is most disappointing in how it treats Bane. As a villain whose characterization is just as good as the Joker's (IMO), knowing that he would never even have attacked Gotham if not for Talia makes him seem much less cool when viewing it from the beginning.