I can't say things about fighters throughout history, there are no real visual records of fighters so on that basis u couldnt really judge the quality of fighters they faced....I knew you'd say that.
Of course it's not nothing. But it's not everything either in the martial arts/fighting world. I hope you don't automatically deem great fighters throughout history and around the world inferior just because they never touched a boxing ring nor have a collection of belts. Can't judge everyone by such particular (and dare I say, Western) standards. (If only kung fu championships existed too.)
I still don't understand what you mean by "proven" and what sort of evidence you need...
If by "professional", you're referring back to heavyweight championships, then I've already shared my opinion on that above.
But anyway, your opinion, my opinion.
by the way the boxing thing is not really a western standard as competitors for the belt come from all over the world, hence WORLD champion meaning that u are currently the BEST in the world and that means going up against others who think they are champions.... I think if you can claim to be the best in the world and have a belt to prove it it gives you some kind of CREDIBILITY...
now what I mean by proven, as I said above if you compete than your a proven fighter, Bruce Lee never got into any tournament nor did he ever compete in anything except for that one time he was in hong kong and he beat some british boxer who was the champion of his college or somin, other than that Bruce Lee hasnt fought any worthy opponent who is on a world class level like Ali...
Ali however like I said before fought monsters and beat them, in his prime he outclassed dangerous opponents and made them seem like they were nothing, i mean Ali survived Liston for a few rounds fighting him blind!!!!
Who has Bruce Lee fought on a world class level that compares to the likes of Frazier, Liston, Foreman?
either way its a stupid mismatch anyway, they are not even in the same weightclass, u might as well do Floyd Mayweather vs Tyson....