Its the same with music, so difficult to find good women singers. They usually just sound nice or beautiful, but without any personality. Of course you have your great exceptions.
See, Pj harvey, Patty Smith, Janis Joplin, black jazz/blues singers, etc...
I think its because women have much more personality problems (or lack of it) because of how men have opressed them in history. It has always been more dangerous for women to express their feelings/opinion/creativity so they are just much more gregarious than us men.