I think the greatness of a player cannot be judged solely by the number of Slams.
First, because Slams have not always been the alpha and omega of tennis like today. Without going back to the pre-open era, one should keep in mind that for 24 years (1972-86), the Australian Open was not considered a major. And during the 70s, many Grand Slams should be asterisked and others do not even deserve the "Grand Slam tournament" label.
Ergo, there should be other criteria such as the influence on the game, the popularity, the longevity, the exceptional nature of certain achievements, etc.
Tennis players who changed the way the game is played, whether it is a style, attitude, or a signature move, are a rare breed.
Nastase for example, won only two Slams, but has 4 Masters to his name, the unofficial Grand Slam of the time. And more importantly, he left a lasting tennis legacy, thanks to his spectacular shots, artistry and panache, he was highly popular and tennis owes him a lot.
Hewitt on the other hand, proved that you don't need to have huge weapons to dominate world tennis. He showed that the mental part of the game was the most crucial and to this day, he's still the youngest ever No.1 player in the world.
And one last thing, considering that there were tens of thousands of tennis players, when should we stop counting? The first 10 ATG, the 20, the 50, the first 100 ATG ?
