Talking about someones win percentage in bodybuilding seems like a week case to make.
First in most sports where a W L record matters the record is compiled in one on one competition or at least one team on one team competition. Not 1 out of 16 or 1 out of 23. In bodybuilding if you enter a show that has 30 competitors and you place 6th, youve beaten 80 % of the competition but it's still a L

Bodybuilding is subjectively objective. In other words there's supposed to be objective scoring criteria but ultimately it comes down to the subjective opinion of the judge as to whether or not you meet the objective criteria.
Also bodybuilders are judged in comparison to not only the other competitors but also to previous versions of themselves. An example would be the old grand prix shows where the same guys would compete against each other in 7 or 8 consecutive shows. One guy is clearly better than the rest but is off compared to what he looked like last week and loses to the guy he just beat who held their condition.
Also, comparing era's, you have to acknowledge that the qualities that drive someone to be the best would prevail. Few men rise above the standards of their time. Arnold and Sergio would've done well in any era. Ronnie wouldve too but if Arnold were to be 27 years old and competing in 2003 he'd look a lot different than he did in 73 and vice versa for Ronnie. These guys would push themselves to do what it took to reach the top given the standards of their time. So Samir won in 83 with weak hamstrings, well nobody gave a shit about hamstrings in 83 but if he were in his prime in 96 you can bet he would've had much better hamstrings. And Ray couldn't beat Lee, Ronnie or Doz but if his prime were in 82 he probably would've been a Mr. O.
IMO you got 4 guys in bodybuilding that are the Mt. Rushmore GOATS of the sport and thats Arnold, Lee Haney, Dorian and Ronnie.
Then you got the next tier guys who wone the big one but couldn't hold on to it or were good enough to win the big one but it just didn't happen: Flex, Vince, Kevin, Nasser, lou, Gaspari, Labrada, Kai and I think Shawn falls into this category along with Zane, Dexter and Samir etc...
Then theres a third tier of guys who were truly fucking great.and made names for themselves but were never ever going to win the big one and thats. Dillet, Demey, Quinn, Christian, Platz, Padilla, Boyer Coe, Ruhl , Roelly, Victor, JOJ, Albert Beckles and on and on.
Long post/it's early and coffee is kicking in.