Agreed, good point! Jones is the last fighter I ever imagined to have to keep boxing well past prime. I always thought he would retire at his peak and then become a rapper! I am not sure if it is financial reasons or if he just craves the lime light but there are better ways of staying famous than getting KO'd by cretins. Many fighters have carried on past their best but as you say very few have lost so badly to such poor fighters.
Mayweathers resume blows away RJJ in my opinion. I don’t even think it’s close. I think Roy’s problem was after Toney and BHOP Tarver n maybe Ruiz his wins aren’t that impressive. The divisions were lacking. Mayweather has a lot of decent to great wins over Canelo, Pac, Cotto, Delahoya, JMM, Castillo, Judah, old Mosley, and more. To get back to ops post RJJ is not under rated he just didn’t have that many decent guys to fight and the ones he did he dominated which he was supposed to do. He didn’t start losing till he was older and lost a step
I rank Mayweather slightly ahead of RJJ, it's arguable either way though, imo. RJJ has the best 2-3 wins, in Hopkins, Toney & Ruiz. Mayweather doesn't have anything to compare, imo. RJJ is the only 1 of the 2 to have beaten a consensus top 10 all time in one of the original 8 weight divisions (Hopkins at MW). As you allude to, Mayweather has the deeper resume as well as greater longevity, and didn't have the dramatic post prime slip & defeats. At their respective primes, as brilliant as Mayweather was, and he was fantastic, I think RJJ was even better, p4p. He just doesn't quite have the depth of resume or consistency of longevity, that Mayweather does.
If RJJ had retired after the Ruiz fight, I think it's possible he could've been rated above Mayweather.