I have read some gay fiction, and I know it can be highly creative. I am noticing that science fiction and urban fantasy are establishing their plots in the field. That's super cool. I have also skimmed the section in B&N, secretly eyeing the glossy covers. I always enjoy gay fiction covers! I half expect to find a haystack and a pair of tight-fitting Levis on every other book. And that's my point. Compared to my own writing, many gay fiction books are largely romantic and stoked deeply in sexual expression to a level that makes mine look like the clueless nerd holding the science books. I don't write romance straight out.
Gay fiction also has a contemporary feel, even if it is set in the past. Maybe it's just me, but gay fiction has a coming of age audience (of which I was once an active member), and often a higher morality or a shamed desire to be freed from the closet. Of course, fine writing and vivid characters and talented writers can be found in gay fiction as in any genre (and can even coin a phrase in American culture: Brokeback). Romance is key. Sex and the freedom to have it are key, too. Plots that lead to those moments are key. I think gay fiction is more gay romance fiction for a young audience.