+1. There's reasons why women can't beat men in just about any sport you care to name. I'm not being sexist here, it's just a fact.
I'm not prepared to say that a woman can never be the world's best pool player, but I'm breaking excellence into its foundational components and I see it as very difficult.
I've watched women's pro pool since the 1970s and when I look at the components of success as I've defined them, I am reminded of how tough it will be for a woman to reach the top: Here's how I see it based on the case history, although I must state in advance that I'm not as knowledgeable about some of the Asian women as I am about the American and European women.
The Break
We've definitely seen a few ladies over the years that have big breaks even by men's standards. The names that jump off the page for me in this regard are Jean Balukas, Ga Young Kim, Kelly Fisher Sarah Rousey, Helena Thornfeldt, and Tiffany Nelson, the last of which hit 29 mph on the radar gun one year at Super Billiards Expo.
Ball Pocketing
I don't think we've ever seen a woman that pocketed balls as well as top male pros, although a few have pocketed as well as middle speed pros. Of course, there's no denying that Han Yu and Siming Chen are raising the bar. The names that come to mind here are Jean Balukas, Allison Fisher, Karen Corr, Kelly Fisher, Han Yu and Siming Chen.
Position Play
In my opinion, no woman that I've ever watched played the patterns or controlled the cue ball like their male counterparts such as Buddy Hall, Ralf Souquet, Wu Jiaqing, Kim Davenport, Darren Appleton, and Jim Rempe. Only a few women ever have been rock solid position players by men's standards, with Allison Fisher, Karen Corr, Robin Dodson, Siming Chen, Han Yu and Jeanette Lee the ones that come to mind for me.
Defense
In my opinion, the only woman player that has ever played defense at the level that would be considered elite by the men is Karen Corr. Even the top men pros will vouch for this, and Karen got around to beating a lot of them, including beating then World Champion Ko PIn Yi at the US Open 9-ball. Still, the gap between the defense played at the top of the men's game and that found in women's pool is very wide. Several woman players have played defense at a level that would be considered middle level pro in men's pool, with players like Jeanette Lee, Jennifer Barretta, and Line Kjorsvik being the most obvious.
Kicking/jumping
There have been more than a few good jumpers in women's pool over the years, especially Robin Dodson. Nobody, in my opinion, kicked like the most elite men. Ga Young Kim certainly kicked at a level that would be considered middle level men's pro, and Karen Corr was also a very classy kicker.
General tactical conceptualization
Once again, Karen Corr stands alone here. She never did shoot quite as straight as Allison Fisher, but always had the edge tactically, which is why their matches always looked pretty even on paper.
In Conclusion
Give me a woman pro that breaks like Jean Balukas, pockets balls like Siming Chen, plays position like Allison Fisher, plays defense like Karen Corr, jumps like Robon Dodson, kicks like Ga Young Kim, and moves like Karen Corr, and then we've got something to discuss. History says that the emergence of such a player is at least theoretically possible, although the training of such a player would have to break the mold of anything seen to date in pool instruction.
Such a player might just contend for a world championship on the men's side. I really can imagine it, but I don't think we'll see it anytime soon.
I don't see this as a gender issue at all, but I see a long and difficult road to success for any woman who wants to be counted among the top few players in the world.