It seems, to me, that one thing which distinguishes genre writing from other fiction writing is that it pays much more attention to plot than to character. Aside from the gunslinger, all of Stephen King's characters blend into one amorphous troubled New Englander who is doing the best they can in horrific circumstances. With no real exceptions, the same could be said for H.P. Lovecraft's characters- I can only really remember Herbert West and Cthulhu, and a whole lot of passages with strings of adjectives along the lines of "clammy". J.G. Ballard, whose writing I adore, even went so far as to give multiple characters the same name, his own name, or in one case simply distinguished them by profession: the pilot, the doctor, etc.
Ballard has been called a great novelist who has never written a great novel, an assessment that I would agree with (with a few reservations). Philip K. Dick, on the other hand, did write a few great novels, particularly VALIS. Nevertheless, he has the same problem as other genre writers- his characters are either him or they're cardboard. He's a lousy prose stylist who wound up writing a few great novels anyway. For this, his legacy is assured.
Or better than that. In this New Yorker profile, Adam Gopnik explains why great genre writers, particularly Philip K. Dick, are so wildly beloved by their fans. In the case of PKD, he's already received the Genius treatment, as Gopnik describes it. I can attest to upscale bookstores in Paris selling deluxe editions of his books. And he certainly has fans who would likely compare him to Jesus, were Christ more imaginative.
Another way of looking at how genre deals with characters is to say this: great literary fiction tells us something about ourselves and about individual psychology; great genre fiction tells us something about the sort of world that we live in, or the potential worlds that we might live in. Gopnik makes the case that Philip K. Dick's work is funnier than is generally recognized, and that it tells us much about the sort of societies that human beings live in as well as the sort that we live in today. Unless societies change profoundly, his novels should continue to be worth reading.