Given your criteria in the OP, it would only be Ali. But if we’re cutting some slack: Jim Jeffries Jack Johnson Jack Dempsey Joe Louis SRR Muhammad Ali Mike Tyson Floyd Mayweather Manny Pacquaio
All-time, who knows. The world was a much smaller place even 100 years ago. And information wasn't as widely shared 50 or 100 years ago. Countries were cut off from global news. Today? Really only Muhammad Ali. And he hasn't fought in 40 years. Everyone knows the name Muhammad Ali and that he was a boxer. Little kids. Old people. Basically everyone alive today. He is a global, historical figure. The rest, they are all really regional stars. Or there are corners of the world who have no idea who they are if you say their name. Or, if they were known in their day, those who knew them are dead or they are long since forgotten by the vast majority of the world's population - if most of the world even knew who they were back in their day. Just Ali, really.
I agree that Ali fits the bill. He was referred to as "the most famous person in the world" for a time. But I also agree that his recognizability decreases with time. Around the time of his death I saw several mainstream articles where his name wasn't even spelled correctly. Joe Louis is up there. Kids today wouldn't know who he was, though, and I see him referred to as "Joe Lewis" in mainstream publications. Tyson, definitely. Foreman, probably, thanks to the grill and his other ads. Even in the seventies he acted on mainstream TV shows that everyone saw, at least in the states. Eubank? No way. No in the U.S. Maybe in the U.K., but not here. I don't even recall him on the cover of boxing mags, much less in the mainstream press. Holyfield was far better known here. Most of the guys mentioned were famous for a time and then forgotten. As far as mainstream recognition, you could go anywhere in America and show people pictures of Joe Biden and Boris Johnson and many people wouldn't know who they are.
Only Ali and Tyson are known in every country on the planet So if that's your definition of global superstar then it's just those two
I think that when you factor in colonialism, a few of the bare knuckle champions would meet the criteria. People would have known who Jem Mace and John L Sullivan were, in any country where you could get newspapers. Even somebody like Tom Cribb or Tom Sayers, would have been discussed from London, to the Cape, the New World, and the Antipodes!
Ali & Tyson are known in villages in Kenya. I've met people who think boxing, UFC and WWE the same thing but they knew who Ali and Tyson are.
The four that have been mentioned by the OP just about covers it but Ali was simply on another level. At his height he was possibly the most famous person on earth.
As mentioned by many here, if it is done on the criterion the opening poster wants, then it is only Ali. If you have the further caveats of at the time and in the Developed world, then the list starts with Jem Mace and then John L.. And the numbers go in the classic bell curve, probably peaking in the 50s sometime.
