Really depends on your definition of "Wrestler" - simply are we looking just at a guy's ability to do a wide variety of moves, take a wide variety of falls, and be able to sell the legitimacy to the audience (unlike a lot of younger wrestlers who simply move from one spot to the next, never selling anything, and looking totally fake doing it). OR are we considering the athletic side along with the entertainment side (promos, crowd reactions, etc). Do we ignore drawing ability and popularity also ?
Since the 1970s which is when I started watching I think the Steamboat and Benoit excelled at the physical side, many different maneauvers, ability to take a variety of falls, always sold the believability of pain, exhaustion, etc to the audience, they made it look real. Steamboat had a good career but he always comes up short in conversations about "the best" all time against guys like Flair & HBK due to his relatively stable, safe, personna. He wasnt as entertaining on skits or promos but he could deliver a great match. Likewise Benoit was always criticized for his below average mic skills and supposed lack of charisma. His athleticism and abilty to sell in the ring helped him overcome a lot of that but as a complete package he always looked a step behind guys like HHH, HBK, Jericho, etc. Jericho has always had a very good combination of promotability outside the ring and ability within but his career has never reached the heights of say Flair or The Rock. Brett Hart was tremendous in the ring, and had a successful run in the 90s in both WWE & WCW, but he was never the equal of Flair & HBK on the mic for entertainment value although they both could come close to him in the ring. In terms of drawing power and longevity HBK falls short vs Flair, but Hogan was a bigger star than all of them but probably the least talented (although under rated) in the ring of anyone mentioned in this post. Austin was a huge star, he also could deliver great matches along with his mic work...is he the best al time, maybe a step slower than Flair, Hart, or HBK in the ring but above them all to varying degrees in drawing power, better than Hogan in the ring by a wide margin but a veritable draw against him in star power, slightly better than Rock in the ring but equal or better on the mic ? Lets not shortchange Kurt Angle... he may have been better than all of them at selling and being believable with a wide degree of offense and ability to take falls in the ring and he was very entertaining on the mic, a major star but the equal of Hogan, Austin, or Flair or Rock, but very close, maybe equal or better than Hart in the ring but with a less resounding sesume (though he has a great resume). Where does Sting fit in ?
It's all too subjective. In the end people have personal favorites for different reasons, it's just too hard to judge.