Kramer's career was hampered by ww2. It's a tough luck but there is really
no way to have him in the mix. Based on what anyway? Couple of slams?
For what is worth, he was luckier than another potential GOAT, Tony Wilding
who died fighting in ww1.
Now Tilden is respectable champion based on his achievements, but he's been
surpassed statisctially by many guys, (Laver, Sampras, Federer, even Pancho
on some level) and no way he can be boat, given the fact he was the first
among greats, and it's reasonable to assume all others who surpasssed him
achievement-wise have also devoleped far far superior game to his, based on
game's evolution. Rosewall never won Wimbledon, and Pancho is even more one
dimensional than Sampras.
So it's Laver vs Federer and I say Laver.
PS I am in wonder why are all Tilden's US Championships titles regarded as
slams, when US Chmapionships became major event per ILTF only in 1924.
His titles there in 1920, 1921, 1922, 1923 are not really "true slams".
Also he won Wimbledon (which was a slam per ILTF at the time) in 1920-1921,
but it was prior 1922, during challenge round era, meaning he won only one
match in 1921 to win wimbledon title. That's 5 asterisks in his resume.
I don't think he truly deserves "king of USO" title.
It is more appropriate for Sampras/Federer/Connors, ie Sampras who has most
finals there.