Its an interesting discussion, though everyone other than Hogan and Austin are difficult to argue for because TV ratings for Pro-Wrestling were non-existant prior to Hogan.
Hogan made pro-wrestling in the 1980s, and his heel run in the 90s nearly buried WWE. When you account for the amount of time he was on top of the industry, as well as money brought in through ticket sales, merchandise, TV ratings, etc... its Hogan and by a very wide margin.
But for the overall highest peak of Pro-Wrestling - The Monday Night Wars and Attitude Era - Stone Cold Steve Austin ruled it and for the 6 years he was on top of the WWE is was the absolute best quality Pro-Wrestling in its history. Period. All of the factors I mentioned with Hogan were never as high as they were with Austin with any era of WWE... even with Hogan in the 80s... but Hogan's era lasted 20 years as compared to Austin's 6 years.
I still maintain that if WWE had offered Austin the right pricetag to have a year-long feud with Hogan back in the early 2000s... it would have banked WWE hundreds of millions of dollars.