Andrew Wheeler went through Publishers Weekly’s list of best-selling books from 2009 and took out everything that wasn’t sf/f. The list of most popular sf/f books is here.
I don’t have a lot to say about the content of the books. You have to go pretty far down the list before you find science fiction. Fantasy and Horror dominate.
Another thing I notice at first glance is that there aren’t that many writers listed once on the list. Most of the slots are books from authors with at least one (usually more) other slot on the list. In Donald Maas’s The Career Novelist (there’s a free pdf of the book at the end of that link, btw) the agent took a look at which of his writers were earning six figures every year, and what they had in common.
He said the authors earning those big bucks weren’t getting it in advances. Most of it was coming from backlist sales, and they had to write about ten books before they reached that point. Interesting stuff.
And no, my book is not on the list. Yeah, I checked.