At 160, I'd take Jones and Monzon over him. The best version of Robinson too. Hagler is pretty much a 50/50 fight, although I favor Hopkins. At 175 most of the elite guys in the history of the division beat him.
Calzaghe couldn't even beat a 43 year old Hopkins no matter what the judges say. Calzaghe would be very fortunate to end the fight in a vertical manner vs a prime Hopkins. But to answer the question a prime RJJ just because of his sheer natural athletic abilities not because he was a superior boxer.
You should have made the poll multiple choice. One fighter that you think can beat Hopkins? He did beat him with one hand. A multitude of fighters in every era could beat Hopkins. Where is this coming from due to his win over Pavlik? He is between good and great. He is more popular for beating lighter guys and I know Hagler did the same. If he would have been fighting like this back in the day, the I think he would be considered great.
From that list... Who I think would beat Hopkins: Jones, Foster 50-50s but I would give Hopkins the edge: Hagler, Toney, Qawi, Leonard Hopkins would definitely defeat: Calzaghe, Hearns
Unfortunately, I have to concur with this. Bob Foster is (in my opinion, I know many would disagree) the hardest single-shot puncher p4p in history, and (contrary to consensus opinion) Hopkins was not a natural lhw. Foster is the only man in 160-175 history I would actually back to stop B-Hop (others may manage it sure, but Foster is the only one I believe would not merely could).