The big discrepancy is because Pre Open Era the best male player's might have only played Wimbledon 2-3 times before going Pro(ie ineligable to play in Slams), thus having a larger pool of former winners.Whereas their weren't as many options available for the women so Margaret Court,BJK,Maria Bueno etc were still competing at 3 or 4 of the Slams year in year out, even before the Open Era. You would have had a lot more female Slams winner's if say Margaret Court went Pro after 2 Australian Open win's and didn't play a Slam again until 68.