Look. I have nothing against them and they deserve their place in history. However it is exceptionally difficult to compare them with modern players (achievement wise) for a number of reasons. 1. Lack of Fitness/Physicality allowed more longevity, thus more achievements accrued. I'm not saying these players didn't take fitness seriously, they did. But not as seriously as players in the modern era and there weren't as many techniques to allow for greater fitness/strength back then. Also, the style of play back then was far less physical and was more skill-based. This can be evidenced by (literally) chain-smoking grandparents in their early 40's beating the world no 1 and some players peaking at a far higher age than they do in today's game and by the success of exceptionally short weak players like Rosewall and to an extent Laver. This lack of physicality and fitness also applies to the first 5-6 years of the open era as well. Rosewall won 15 pro majors and 4 open era majors, meaning that if there were 4 pro majors a year, Rosewall would have won around 24 majors. That number is just unapproachable in today's game. Rosewall was able to attain such an impressive figure because the lack of physicality first allowed such a short player to succeed and then allowed him to succeed long after his physical skills diminished. 2. How much is a pro major worth? They were usually only 8-player draws, making it easier and less taxing to win a pro major. Also, no such thing ever formally existed as far as I know and there certainly wasn't the same amount of prestige attached to them. Furthermore, it is subjective to judge which 3 tournaments were worth the most every year and some would argue that some of the pro majors were worth more than the others. 3. Lack of proper ranking system No official ranking system till 1973, so previous rankings were subjective. Furthermore, even the year-end rankings published by experts don't tell us who was world no 1 each week on the rolling calendar. Weeks at number 1 and year-end no. 1's don't fully correlate. 4. Lack of depth. Only about a 100 pro players generally from far fewer countries than they come from today. It does make a huge difference. It's not necessarily that just everyone but the 100 best players are excluded, its more like randomly removes 24/25 players including the top players. (Well it's actually sort of a combination of the two). 5. Increased value of Head to head Due to smaller draws, pros played each other more often, thus increasing the importance of match-ups and beating a certain player versus beating the field. The long series pros played against each other also did the same thing. Again, I don't think the players from this era were bad. Just that their accomplishments are distorted and hard to compare to those of modern players (starting from the mid/early 70's with Borg and Connors). Therefore, when I rank players, I rank them from separate eras. Open era (73 onward) of which Federer is the G.O.A.T, and the pre-open post World War II era of which either Gonzales or Rosewall is G.O.A.T. P.S, I'm aware of the eras before that. I wish some people here discussed players from those eras as well.