I wasn't the one running the game, but I did read one of the backgrounds for a game I was going to be in. The player talked about most of what was in it, so it's not like he was keeping it secret, and the Storyteller (this was a World of Darkness game) half-jokingly said the background read like a lesbian porno.
Which, upon reading it, that's exactly what it was. It was like something you might see late night on Cinemax. Ahhh...at least, so I've been told.
And that wasn't the first female character he played along those lines. However, he's since heard my ire and kept himself in check. He's currently playing a woman in the Ravenloft game I run, but there's been no problems.
Other than that...I don't believe I've had/played with many opposite gender from the player type characters. A few of my friends and I have bandied around various character concepts that we'd like to play, of which a few were women, but other than that, we haven't played more than one game here or there over the years where the gender of our character was different from our own. Those times, along with the character concepts that never saw the light of game, weren't particularly of a bothersome variety.
Still, it does seem a common problem, and I've heard about games my friends played in that I didn't, where they had the bad, stereotypical opposite gender kind of characters.