To be the best skier of all time, you truly have to change skiing, the way people see it, and change it for the better too.
The people that fall under this are:
Scott Schimdt
Glenn Plake
JP Auclair
Eric Pollard
Pep
Seth
I see Tanner, Andy Mahre, and many others on the way to be a part of the list above.
The best skier would prob have to be pollard. He's influential in bringing skiing back to its roots with natual features, skiing switch, and really pushing style to be more important than spin to win and competitions.