Hogan, Austin & The Rock should be top 3. I don't care what anyone says. Sure HBK did a lot for the business, but like someone mentioned he never sold as many seats as those 3. HBK also played backstage politics for almost his entire career, even after his return in 2002. Hogan revolutionized the wrestling industry, if not for Hogan, WWE would be dead long time ago. Same goes for Austin & Rock, if not for Austin/Rock, WWE would have died and lost the monday night wars, no doubt. Rock/Austin saved WWE's ass during attitude era, without those two Vince would be working for Ted Turner today.
Do not judge this list by wrestling ability, WWE is, was and will always be about entertainment and making money. Wrestling is on the bottom of their priority list. If WWE made a list of top 50 'wrestler' NOT 'superstars', then yes I would definitely not mind see HBK on top.
I know Hogan also played backstage politics, but he also was smart and made good choices. He jobbed to people when he knew it was worth it and would help the company, he put over Undertaker, The Rock, Brock Lesnar and even Edge