The best female stand up comics are either ugly, or had circumstances where they had to be legitimately funny or they weren't going anywhere on the circuit. Now the bar is set low because of political correctness, or simply guys wanting to get into their pants by moving them up the ladder.
Cloris Leachman, Joan Rivers, Phyllis Diller, Lawanda Page, etc.... all had chops because they were ugly to average looking broads in an era when guys weren't afraid to say it if someone was terrible. If they couldn't hang, some talent booker was behind the scenes like - "This bitch is terrible, what's Rickles or Pat Cooper doing next week?".
Likewise, a lot of the better female talent I see now a days is from the urban/black "chitlin circuit". Those crowds don't have the same PC/Guilt hang ups that other places do, if someone is terrible, they're getting booed, hit with a chicken wing, etc....