Personally, I think a lot of the 'pull' of gay porn deals with the incredibly cute porn stars who are featured in it.
Heck, even lesbians watch gay porn from time to time. Many people, regardless of gender or orientation, has one of those moods where they want to see men with men.
Maybe it's the fact that it's two gorgeous guys who are into each other, or maybe it's just all the masculinity they show, but whatever the reason be, gay porn gets a lot of people hot under the collar.
There is something remarkably hot (and beautiful) about watching two men go at it on camera-even if you're not a gay man.