You know what bothers me about this thread (and many others like it)? Why isn't this thread called "Inception or The Dark Knight or Memento or The Prestige, which do you prefer?"
I think Inception had the rather unfortunate burden of being Nolan's next film after The Dark Knight. Thematically and in most ways it's very dissimilar to TDK, but of course people are going to hold it up to that shining example of Nolan's pedigree.
If this movie had been released before TDK, it would've gotten the same attention as, say, The Prestige. The Prestige was an original film that had big name actors attached but didn't quite catch on with moviegoers despite its high quality. I actually still like it more than either Inception or The Dark Knight, but this thread certainly doesn't want to include it. Why? Because of the of the popularity effect that came with The Dark Knight's phenomenal success.
Inception is just like The Prestige, except it had the luxury (or misfortune) of coming after The Dark Knight. It makes me wonder if The Prestige would have gotten more attention if things were reversed and it was released now.