Ranking across decades is fun, but probably not fair or accurate or realistic.
Some very notable names, of course, are Smith, JB, and Bruce. However, there are other names that perhaps should be notable, but are often overlooked:
Others have pointed out that Menhert, who is not normally mentioned, won two Olympic golds -- in 1904 and 1908. That puts him in rare company with only Smith and Bruce.
Robin Reed (1924 Olympic gold medalist) was apparently extremely good. Allegedly he never lost a match to anyone at any weight class.
For more than 50 years Jack van Bebber was the only wrestler to win three NCAA titles (plus he was undefeated) and an Olympic gold.
Lee Kemp, I believe, is underrated, although he gets more attention than the previous three athletes.
Etc etc