Fortunately I don't get approached much by gays in nightclubs, although it happens every once in awhile; somewhat less rarely one or more will try to get my attention in the supermarket, bookstore, Starbucks, etc. It's always in a semi-creepy way, like how the average dorky guy would eye over a girl in public. The one exception is masculine gays -- they never give off that creeper vibe, aren't overly eager to push themselves on you, and in general are easy for guys to get along with (no girly vocal inflection, no histrionics about how disobedient their pet poodle has been, etc.).
Admittedly I'm only basing my impression of the guyish ones on three regulars at a nightclub I go to (and Freddie Mercury), but it's such a world apart from the makes-your-skin-crawl vibe of feminine gays that I think it's enough data.
Clearly creepiness is not something inherent to having a Y chromosome, nor even inherent in playing some male-like role -- again, it's the feminine gays who creep others out. It must have to do with who is in a more desperate situation. Among straights, that's guys: on average, they want it more than girls are willing to give. Especially since only some fraction of guys get most of the attention from girls, the leftover fraction are more willing to do something desperate and potentially creepy because at least they'll get noticed for a moment or so, rather than remain completely invisible.
Among gays, there are many more feminine than masculine ones (I'm not sure if this is the same distinction as "top" vs. "bottom"). Since there are therefore so many feminine ones fighting over a handful of masculine ones, the former are more worried about being shut out or invisible. Hence, they're willing to make a riskier and potentially creepy move to get noticed at all.
According to this logic, the more invisible the person believes themselves to be, the creepier they'll act. One reality check here is variation in behavior by age -- all else equal, middle-aged gays are not going to command as much attention as 20 year-old ones. The creepiest gays I've ever encountered have always been middle-aged, which in their case means over 30. Their vibe is about 1,000 times more disgusting than that of the "dirty uncle." (Tim Gunn is the exception that proves the rule.) Even feminine gays, if they're under 25 or so, don't really follow or pester you in nightclubs, as much as they may try to make eyes at you in Urban Outfitters or Barnes & Noble. They figure, "There may be a surplus of feminine gays like me, but whatever, I'm still young and have plenty of options, so I don't need to act so pathetically."
I'd also predict that the gay culture is creepier in a place like San Francisco where the median male is about 35 years old, compared to a college town where the only gays are under 25. The latter might be more promiscuous, but I'm talking about the overall heebie-jeebies vibe they give off to straight guys.