I wasn't picking Benn to beat Jones, just giving an example of a really hard puncher. I pick Jones to stop Benn early too. But I would have been a lot more comfortable with this pick had it happened!
I think that the problem with your statement is that you don't define "best ever." Do you mean best ever in terms of best boxer of all-time? If you do, then you're clearly wrong. RJJ was a great boxer, but he doesn't rank anywhere near a SRR, Ali, ect. Where RJJ could very possibly rank as the best ever in the ring is as an athlete. He was so freakishly strong and fast at his weight that he could overcome his lack of pure skill. His style was built entirely around maximizing those athletic assets to win. Please don't confuse that with being a great boxer. Unfortunately for RJJ, he never had a foil that was great to test himself against. As it stands, there are many p4p fighters I'd pick to beat Jones, but I can't think of any that had his athletic ability.
If we're picking one fighter to go up against everyone else in some kind of equal P4P tournament, I would be more confident in taking Robinson, Ray Leonard, Duran, Ali, and maybe Whitaker than I would with Jones. That's basically meaningless though, as it is entirely impossible to determine how one fighter does against every fighter throughout history set at an equal size.
Head to head he has an argument for the greatest fighter in history pound for pound. At 168lbs in his prime he it is hard to pick against him.
i'm a charter member of the rjj fan club but it's real hard to call someone the best ever at something that so many greats have competed in. i feel that its easier to judge based on generations (preferably the one you live in so you have a frame of reference) but even then its tough to call someone the "best" of their generation. i think its easier to get people to agree that he is one of the best of his generation, an atg, first ballot hof....unless your name happens to be rico