Where's Lendl? Seriously, we wouldn't have the slow surface grindfests we have today without him. If this period of slow surfaces and hard-hitting baseliners obsessed with fitness continues for another decade, the father of that kind of tennis should certainly be considered the most important ever.
None of the guys on your list are repeatable. They're all one of a kind. How does that make them important? What did the contribute to the sport but popularity, fleeting popularity...
I have come to the conclusion that I simply don't know what I don't know.