Every genre writer's dream (or at least this genre writer's dream) is to write a work that attracts readers from outside the genre, without compromising its essential genre nature. In fact, to bring them in, to show them what the point of the genre really is, and get them to appreciate it.
I've not read enough Westerns to know whether McMurtry's Lonesome Dove is a representative Western, but it sure is a great novel. It's pretty elemental: men and women in rough, hard-to-survive country, hard because of the unsparing environment, and hard because of other human beings. Some characters you have invested real feeling in get killed offhandedly, the way real people did, and do, die. Victories are local and temporary, and savored all the more for that. Defeats are large, and often final. The characters are compelling, and often funny as hell. They understand what many of us have forgotten: our most important duty in this life is to entertain each other.
McMurtry does it without elaborate literary references, mythic structures ("mythic" in contemporary fiction means "unbelievable characters with tortured syntax"--run if you see the word used in a review), or "fine writing".
Now, McMurtry is not purely a writer of Westerns, though he is a Western writer, so it's not like he's clawing his way out of the corral. But he's decided to play to what makes the genre appealing (particularly a stoic nobility brought out by the harshness of circumstance), commenting on it at the same time (Call, the most stoically noble of the characters, is disliked and suspected by all women, who tend to perceive too clearly what it is he had to give up to be who he is), while letting us share in the genre's inherent energy (you can see why the men respect Call, obey him, and instinctively want his approval, while understanding why someone who does not depend on his skill and authority might be less taken in--even Darth Vader eventually identifies himself to his son, and Call...well, you'll just have to read it and see what Call does with his own unacknowledged son).
Science fiction is a much bigger playground than Westerns, so it's natural that many more writers can play there and nowhere else, and have successful, productive careers. But sometimes it's worth trying to take your ball and play somewhere else, using the skills you learned there.
That was my ambition with Brain Thief, certainly.