As far as the great clay players of all time here are some candidates in no order.
Rosewall-Rosewall won a ton of French Pros, many of them on red clay at Roland Garros. He also won the French Champions (now the French Open) as an amateur and the first French Open in 1968 over Rod Laver. And you can add a lot of other top clay tournaments that he won.
Nice list, I'll add Vilas, Trabert, Gimeno (for a while in the mid 60s he was able to beat both Rosewall and Laver on clay). I'll also add the Dohertys and Tony Wilding, they dominated Monte-Carlo when it was the greatest clay tournament.