I'm not sure it's fair to compare what Margaret Court, or any of the other old greats like Suzanne Lenglen, Helen Wills-Moody or Maureen Connolly, did with what any of the current stars are doing. The circumstances were completely different. All they could do was beat those they were up against on the surfaces they were presented with.
They were all great tennis players, just like Martina Navratilova, Chris Evert, Steffi Graf were, and like Serena Williams is now.
I don't think you can crown anyone in any sport as the greatest of all time, because things evolve and change, and things like training methods and equipment are vastly different now from what they were 25, 50, 75 years ago.