Women More Versitile Players Than Men?

At the end of the day, are the Williams sisters better players than Rafa and Rog, who only play singles? And if Rafa and Rog *did* play doubles often, would their singles careers suffer or would they also thrive in doubles (whether they played together or with other partners)? Attached is an old article describing a time when Rafa played against Feds, in doubles! This year, both of the Williams sisters could not win singles, but one did and the other was runner-up. Additionally, they did win the Ladies' Doubles. And get this, one of the losers of Ladies' Doubles, Sam Stosur, did win in Mixed Doubles with Bob Bryan, who made it to the Men's Doubles semi's with twin Mike. Usually you're a doubles specialist or a singles player. Rafa does play doubles here and there, usually paired with his buddies Feli Lopez, Tommy Robredo or Carlos "Moyini" Moya, but Roger rarely plays doubles. Is Feds just selfish? Most of the top male singles players do not really play doubles, or succeed in both. Interesting that there are generally more top female singles players who play both singles and doubles than men. Why is that?