Hmm. I guess I'm an anomaly on this one--none of my gay friends are guys I wanted to sleep with, and I think only one or two of them might have been interested in me that way. One of my better gay friends was a guy I went on a date with; we were both not the other's physical type, he was just out of a relationship and not over his ex, I was just out of the closet and rather hesitant about dating, and a number of other things that make us much better off as friends than boyfriends. I have significantly more straight friends than gay ones, but that's not surprising because there are so many more straight people than there are gay ones. Actually, to the best of my knowledge, more of my friends who would have liked to sleep with me are straight women than are gay men--including my best friend from college.
There's also the fact that my two closest gay male friends are guys I befriended while we were all still in the closet, including both my best friend from high school and one of my roommates in college.
Long term, I've typically had fairly even numbers of guys and girls as my closest friends (though in college it did skew a bit more towards the girls), but my second circle of friends--the people who are more than just acquaintances but aren't the sort you call out of the blue to see if they're free to do something--have been primarily women. I've always felt that part of it had to do with hierarchies; men and women in social groups often establish their pecking order within a gender, but there isn't the posturing for position between genders. Dealing with the chest thumping of some guys was just so much more draining than dealing with the girls, who I'm sure were doing their own version of it but which didn't directly concern me. I've long joked that my life is a sitcom, but it was pretty bad during college when my best friend asked me out, I turned her down, and she started dating someone else while a mutual friend of ours really wanted to date her. *That* guy got to be really irritating in trying to one-up me all the time in front of her, hoping to get her to notice him. I never had to deal with my female friends trying to one-up me for status.