When Christopher Nolan is good -- and Inception looks like it could be very good -- he does, in a way, what Jonathan Letham does. That is, he takes genres that are, usually, cheap, and he takes them seriously (just because he actually does find them interesting) and gives them seriousness (just because he is serious), and ends up producing something that is really amazing.
Both Memento and Motherless Brooklyn, for example, start with a straightforward genre, add a formal element (the reversed narrative for Nolan, a narrator with Tourette's for Letham), and then tells a story. The formal element is a limitation that at first sounds like a stunt, sounds like it's going to be interesting but ultimately a cheap trick, and the genre just is what it is, but then they use those structures and the limitations of those structures to tell a really compelling, insightful and interesting story.
I get the impression, too, that both of them kind of do want to be pop, genre writers. A part of Letham wants to be Philip K. Dick. A part of Nolan wants to be Steven Speilberg. They love their genres, and aren't worried about being perceived as serious. They are serious, but not self-serious. They're not like Jonathan Franzen and M. Night Shyamalan (respectively), who seem to need to be thought of a certain way more than they need to produce art that they like. One gets the sense, and maybe this is wrong, that Nolan and Letham produce this kind of work because this is who they are, this is what they love. They seem comfortable with their work -- both the avant-garde, experimental aspects of it and the mass culture, entertainment industry aspects too -- and like they don't feel the need to justify themselves.