Even a past his prime Gonzales could beat the very best. In February 1970, with Laver at the peak of his powers, a 41 year old Gonzales beat Laver 7–5, 3–6, 2–6, 6–3, 6–2 in a $10,000 winner takes all match in Madison Square Garden. It's like Agassi today beating Djokovic by the same score in a winner takes all money match. Of course, Agassi is long retired while Gonzales was still in the top 10 when he beat Laver in 1970.
We have no way of knowing really, since Emerson constantly turned down the chance to turn professional until finally doing so in early 1968. When players like Gonzales, Rosewall and Laver turned professional, their games went up to another level. By the time Emerson turned professional, he was already slightly past his prime, his prime being around 1961-1965.
I believe Laver won 38 and Gonzales won 21.
Gonzales was the best player in 1952, and was utterly dominant from 1954-1959, barring a scare from Hoad on their 1958 tour, where Hoad led 18-9 at one stage before Gonzales came back to win 51-36.
Gonzales hugely scaled back his tournament play in 1960, but dominated the World Series tours before going into semi-retirement. Gonzales played a few more tournaments in 1961 (including winning the US Pro for the 8th time in 9 years). In 1962, I don't think Gonzales played at all as he was in retirement and Rosewall became the top player. Gonzales started returning in a few tournaments in 1963 and increased his schedule a lot in 1964, but was past his prime by this stage, although still capable of rolling back the years on his day.