Oh dear...
I think the problem is currently the comedy market at the moment is male dominated so the chances of the best comedian in the world being female is quite slim.
However, comedy is about relating to people. If a female can only relate to females then yeah, to a bloke the humour isn't going to be all that good, the same goes for men who only can relate to men.
Also, there are two types of female comedians (as there are male comedians!), the actor, and the stand up (and the writer, so three types I guess).
Yeah, there are few female stand up comedians in Britian (where I'm currently typing from) but despite the small market there are so fab ones such as Jo Brand.
And then there are the actor/writer comedians which there are more of, a wider varity of talent of, but then there are some out standing ones like the great Victoria Wood.
Victoria Wood is a good case study as she plays to her stengths. She's a musician, so she makes that part of her act, she's a script writer, so she'll write parts for other people who are comically skilled to play (as well as doing it herself too), also she does stand up and has her own style. If she wasn't good at all these things, she wouldn't do them.
Sure, some try too hard and it shows but so do some male comedians too. It's just more noticable for the women as there's more of a chance than blokes that they'll have a chip on their shoulder the size of a fish supper.