This is a hard choice for me. There are pleanty of wrestlers who did it for the time-frame in which they existed.
Ultimate Warrior completely dominated Hulk Hogan in terms of popularity while he was around but he clearly proved he didn't have the business sense or lasting power in the industry.
Hulk Hogan, one of my personal favorites. But we consider it in terms of actual numbers, he falls to about 3rd-4th.
Undertaker, revolutioned the "produced" aspect of wrestling. His matches, gimmicks caused wrestling special effects and camera work to become as professional as every other aspect of the business had to be.
Bret "Hitman" Hart, what do you do if you have a gimmick thats quickly failing and a wrestler who isn't this jacked-to-**** roid monkey? Introduce rivaliries on a grand scale. Bret might have been a great wrestler, great with the mic but he will always be remembered for the feuds he had. No one was better to throw into an epic struggle (as good or bad guy) than Bret Hart.
Stone Cold, no one said a man in black trunks could do anything. Sure, he got tired and old eventually but while he was on his rise, what he did for the WWF and the business in general puts him above Hogan in terms of value. Hogan established wrestling, this is true. But Stone Cold also had much more shows, PPVs, larger audience and more exposure to the world than Hogan could have possibly been given in his prime.
The Rock, same as the above just afterwards. Everyone knew mic skills were important but not only did he show that with stunning quality he also spawned the greatest fan reactions I have ever personally seen.