Your criteria for placement is whatever you want it to be. Here are my picks.
Andre the Giant. Don’t see how you could justify leaving him off.
Hulk Hogan. In the 80’s he brought pro wrestling to the mainstream masses. Pro wrestling’s first true mega-star.
(Now things get a little murky.)
Ric Flair. The longevity of his career as being a major headline act is astounding. Seems he did everything you could imagine as a professional wrestler and changed with the times as needed.
One left and it has to go to **Stone Cold Steve Austin **(sorry Macho Man) and I’m not even that big a fan. He wasn’t the first but he changed the dichotomy of heel versus baby face. He was so bad that the fans loved how bad he was. He brought in the soap opera back story line as he launched the transformation of Vince McMahon into the cartoonish over the top Mr. McMahon. Having said that, I can see making a case for putting someone else up there (Savage or Foley most likely.)
I didn’t include any of the old-timers such as Gorgeous George, Lou Thesz or Bruno Sammartino cause I just didn’t. I think my choices are pretty solid though.
Have at it if you will.