Swag what you have to realize is all this is being said with hindsight when Wilder knocked out Helenius in 1 round which is quite a decent win considering Helenius with 6 days notice gave Joshua a rough night. No one was saying Wilder was past it and Joshua was an underdog vs Wilder at the time and Parker certainly was being an 8-1 underdog. I think the fact that Parker beat Wilder comprehensively and its the most accomplished Heavyweight Parker has ever beaten and the fact he was a massive underdog it has to be number 1. Now I'm not saying Wilder is in his peak anymore he clearly isn't but taking everything into account above and not looking at it with hindsight it's number 1 for me as I said. I don't see how getting dropped twice ve Zhang and winning a controversial decision vs Ruiz is better than 12-0ing Wilder who he was an 8-1 underdog against.
Zhang was weirdly overweight against Parker, either had a lazy camp or was injured and unable to train. Had Zhang been a bit younger (say from Hrgovic or Joyce 1) the MD loss would have been a Zhang win imo. Many/most thought Ruiz beat Parker or at least drew. Many/most thought Chisora beat Parker the first time. These are his top 3 wins on ability for me but none were conclusive. His win over Wilder was impressive based on 1. the margin/ease of victory 2. his pre-fight status as a 5/1 underdog. But Wilder was two years removed from his 2nd KO loss to Fury and was finished. On ability I'd rate Hughie and Takam more highly than that version of Wilder, who also gave Parker close fights.
Zhang was conclusive. Yes, Zhang came in 10-15 lbs heavier. But i would argue even Parker came in heavier than he should have. Zhang had just ko'd Joyce - he had never been in better form. I don't think we should downplay this win - Parker took on Zhang when virtually no one else wanted to.