To be fair, I think Martina in tennis is much like Kareem in basketball. Very good for a very long time, but a relatively small peak of true dominance. I'd take prime Graf or prime Serena over prime Martina as I do think they are both just better.
But that is where these things get interesting. I mean are you looking at peak dominance, longevity, stats, winning, physical stature, etc. So many different ways to look at this sort of thing.
If we just stick to Americans, I think my 4 would be Serena, Hamm, Taurasi, and Ledecky
They to me add the right mix of main stream popularity to all time great play. I never saw Babe obviously so I didn't include her and Biles basically getting the yips and quitting on her team was enough for me to go with Ledecky over her.