Just because it's over 2 hours doesn't mean it's overlong.

I would like to think that Nolan will be considered a great director, 20 years from now, and I think there is evidence to support that hope. His movies have made over $1.6 billion in the US. He's received three Oscar nominations (though admittedly not for directing), two nominations each from the PGA and the WGA, which, again, weren't for directing, but, then again he's received three nominations from the DGA which were, obviously, for directing. He has three films many would consider classics (Memento, The Dark Knight, Inception) and others (Insomnia, Batman Begins, The Prestige) that have very devoted followings. And as for the Dark Knight Trilogy, its influence on the mainstream cinematic landscape has been a major, and some would say, beneficial one.

All of this in 15 years (since he started in 1998).