Either Bickham or Swain. In all seriousness, this is a very tough question. I have a few names in mind, but I'll have to give it more thought before I post them.
In terms of technical expertise, I think Anthony Burgess ranks near the top, especially his later works (Earthly Powers is a favorite). There's also John Hawkes, whose themes I don't like, but whose prose is amazing. Peter Matthiessen is terrific, too. (I'm trying to avoid mentioning Nobel Prize winners - they're too obvious.) James Joyce, of course. Nabokov. There are more, but I can't think of them all now.
As a recent Nabokov fan, I have to ask, why does it seem like Dostoevsky and Tolstoy are both more esteemed than Nabokov?
It might have to do with accessibility. The prose of Tolstoy and Dostoevsky isn't difficult to understand. On the other hand, Nabokov's prose can be hard to follow at times; he also uses a lot of uncommon words. So I think a lot more people have read Tolstoy/Dostoevsky than Nabokov. As an aside, Nabokov thought Dostoevsky was a bad writer*. On the other hand, he called Tolstoy "the greatest Russian writer of prose fiction" in his Lectures on Russian Literature. Coming back to the question at hand, as of right now, I'm leaning towards Faulkner. He has written some amazing novels, such as The Sound and the Fury and As I Lay Dying. In fact, I consider both of them to be among the best novels I've ever read. * Here's his quote on Dostoevsky (also from Lectures): "My position in regard to Dostoevsky is a curious and difficult one. In all my courses I approach literature from the only point of view that literature interests me-namely the point of view of enduring art and individual genius. From this point of view Dostoevsky is not a great writer, but a rather mediocre one-with flashes of excellent humor, but, alas, with wastelands of literary platitudes in between."
I started from the beginning of his career and am working my way to today. So: V. Crying of Lot 49, Gravity's Rainbow, Slow Learner, Vineland, Mason and Dixon, and so on. It makes more sense this way, also you see his evolution as a writer better. I say this, though, if you only read one Pynchon novel, make sure it's Mason and Dixon. I'm used to Pynchon's writing style by now, so I might be biased. But Mason and Dixon is, I think, perfect. I can't think of anything I dislike about that novel. Every page is flawless.