I think its a lot more common fantasy for women than they are willing to admit, either due to social pressure to hide homosexuality in all its forms or that they feel they are the only women that feel the same way aka being turned on by two men having sex or even kissing and being intimate with each other. Lesbianism is pretty much accepted as being able to be a big turn on for heterosexual males thanks in large to it's big acceptance in mainstream media through many comedy shows, comics, movies and television. Women being turned on by gay sex though is very rarely if ever highlighted in any of these forms of media, at least as highly publicised as lesbianism and bisexuality for straight men.
But the short answer is yes, I think that there are many, MANY heterosexual women who love and are turned on by gay men and gay sex. In fact, Queer As Folk's core audience was in fact straight women just as Sex In The City was predominately gay men.