WWE, no matter how badly you bash it and criticize it, it still remains the planet's most watched and most well known wrestling show. We must not take this lightly, if you go outside to the hundreds of wrestling fans, they will (most of them) say that WWE is their most watched wrestling show, and this excludes the more learned fans (those who know wrestling outside the boundaries of WWE only). So why would Sting, abeit being such a renowned wrestling in pro wrestling, never reach the likes of WWE's stars? Very simple: lack of credibility. I agree that Sting berng in the top fighters from all the world, but WWE is the place where their legacy will shine the most. Just look at guys like Stone Cold, The Rock, Big Show, Chris Benoit etc. hell if they were ever in shows like TNA, NJPW etc do you think people would actually care? No. The very reason they have gone so far in their career in terms of popularity is due to the fact that they worked for the WWE.
A recent example would be Daniel Bryan, I saw him wrestle at ROH before he stepped into WWE, he was a great wrestler back there, but you never heard his name mentioned here much, neither did you hear him in wrestling forums as such, but after his bursting into the WWE, look where he is now. He is known by the greater masses of wrestling (and WWE fans) than he was ever before. Why? Because I think what WWE does is "distributes" the fame and achievements of the wrestlers and makes them well known. They extensively advertise the wrestler until even the most recent wrestling fan can say "Oh I know Daniel Bryan, he's the guy who works at WWE...."
But this cannot be said for Sting, the only reason he is talked about so much is because of his impact at WCW and eventually getting back into the business with the help of TNA, but aside from that, very few people "know" Sting's legacy in pro wrestling. The first thing that comes up in their mind is a flashy guy with a jacket and facepaint, thats all. I'm not saying EVERYONE think of him this way, but trust me, a whole majority of "wrestling fans" do, especially WWE fans. Me myself, I got to know more about Sting through research, you really think I could know so much through what I just watch on the TV alone? Never. Its kinda weird because I used to confuse Jeff Hardy with Sting (mainly due to the facepaint), but you see? If Sting, as you said, even if he worked for a year, heck maybe even half a year, and he got distributed well (advertisement, memes, blogs etc.) he could've been a major attraction to a whole lot of fans.
Its not necessarily "being in the same league", because we both know that Sting IS in the same league as the guys such as Stone Cold, Cena, Hogan, but its more of a "getting well known" factor. In today's world EVERYTHING depends on how well know you are, from musicians to celebrities, everything depends on how and to what reaches your influence goes. So far as we know, WWE is the world's most well known wrestling plant, how can Sting, being such a historic wrestler, achieve great success like The Undertaker and Shawn Michaels without stepping in the business? He can't.
So for conclusion, Sting, unfortunately, despite his great career at WCW, didn't get to be in WWE, or else I'm sure he would be far more credible in the eyes of many wrestling fans than he is now. And he doesn't belong in Top 10 most well known wrestlers of all time. You can ask non wrestling Fans and I believe none of them would know who Sting is.
BQ : Dean Ambrose.