So do we simply take the slam numbers and make this conclusion? But what about women, say Court of Graf with more slams? What about old timers who were not allowed to play in slams? Numbers are easy, but we think there is more to it than just numbers.
Actually if you look at the times, things like percentage and put all the total numbers in proper context you can make some logical conclusions. I do think that just looking at the fixed number of majors is deceiving because, as you wrote, the players of the past weren't allowed to play majors for various reasons at time.
I also think that in this case it is reasonable to say a female player may be superior to a male player relative to the competition.
I would probably pick the best male and the best female however.
So a Margaret Court with close to 200 tournament victories, a Grand Slam in 1970 and 24 majors is a reasonable choice. So is Graf, with 107 tournaments won and 22 majors plus a Grand Slam in 1988. Navratilova has 18 majors and 167 tournaments won. Evert, also 18 majors and I believe 154 tournaments won.
You can go back further with Suzanne Lenglen, who was almost unbeatable. Helen Wills, Alice Marble and Maureen Connolly who I believe won 9 straight majors including a Grand Slam.
Bill Tilden won eight majors out of eight played at one point at his best. He was almost unbeatable in the 1920's and was still super into the 1930's. He won about 161 tournaments in his career and ten regular majors plus three pro majors for thirteen majors.
Don Budge won the Grand Slam in 1938 and was a superb player.
Fred Perry won a lot of majors including three straight Wimbledons.
Jack Kramer was unbeaten in his head to head Pro Tours and was a tremendous player. A number of experts thought he was the best ever.
Pancho Gonzalez was the dominant player of the 1950's and was a super player. Gonzalez won about 121 tournaments in his career.
Ken Rosewall won 136 tournaments and if you include Pro Majors won 23 majors. He was still winning into the late 1970's and was able to defeat Vitas Gerulaitis for example I believe when he was over 40.
Rod Laver won two Grand Slams in 1962 and 1969. He also won a Pro Grand Slam in 1967. Laver won about 199 tournaments in his career and about 19 majors if you included Pro Majors.
And of course there is Borg, Connors, McEnroe, Federer and Sampras. I'm too lazy to list all their accomplishments but there are many.
I would love to say Bitsy Grant is the GOAT just because I'm always amused by the name but I can't say that. But apparently the guy was pretty good, all 5'4" 120 pounds of him. lol.