I'm not sure which is worse: his impression of a woman or his impression of Frank'n'Furter.

While Curry is the first and definitive Frank, I have heard/seen several other actors play the role over the years, and they all had enough voice, presence, and charisma to at least put their own spin on the character. No wonder they put that stupid headress on Cox, that's the only way to make him noticeable. And his voice... I've heard drunken 3am karaoke better than that.
It's incredibly symbolic of what the old gay and lesbian culture has become in the hands of the queers. On the one side
absolute
pleasure, on the other, a woefully inadequate wannabe desperately trying and failing to fill Tim Curry's stilettos.