I'm not sure how atypical this is, though (at least post-WWII).

Who in the 90s was a true superstar? Tyson, Holyfield, De la Hoya, RJJ. Can't think of any others. I don't think Lennox Lewis was ever a recognizable name to non-boxing fans in the U.S.

80s: Tyson, SRL, and to a lesser extent Hagler, Hearns, JCC (and he's borderline outside of Latin America).

I may be missing a couple but I don't think there have ever been more than maybe a handful at a time during my lifetime.