If you're talking "All Time" then you're looking at guys like Buddy Rogers, Gorgeous George, Bruno, Harley Race, not too mention Nick Bockwinkle.....that's awfully tough.
If pro wrestling had a Mount Rushmore Hogan, Flair, & Vince McMahon would be on it.
Where does Sting rank....that's tough.....He's Top 50 all time, maybe Top 30, I can think of a lot of guys I would rank ahead of him (Hogan, Flair, Bruno, Dusty, Austin, Savage) and a lot Id rank below him (Nash, Luger, Ultimate Warrior, Goldberg, Lawler, Barry Whyndam, Ricky Steamboat). Sting had a great look - that he morphed into another great look. He very early on developed on the mic and now is very good, maybe not Flair-Austin-Rock-HBK good but better than a lot of other top guys like Brett Hart, Luger, Hall, Randy Orton, etc....and in the ring he was always excellent, much better than the overwhelming majority of "muscle guys" and maybe in his prime just one step below the truly best main event level in ring performers.
I think somewhere in the Top 40 makes sense. It's hard to say exactly where, I can maybe see him in the Top 20 or Top 25 but with so many great legends of the past like Rogers, Piper, Harley Race, etc it's tough.