I am a professional boxing writer who has to vote on who gets into the Boxing Hall of Fame so this question certainly resonates with me. With your mention of Harry Greb it is clear that you know your boxing because based on his record and opposition there are many of us who believe he is one of the greatest of all time. But is it legitimate to rank fighters from different eras-- or teams. Not if you imagine "legitimate" implies that there is some science behind it. But I think it is legitimate if you take your ratings with two grains of salt -- maybe 3. You look at a boxers overall ledger and whom he or she competed against. Fighters from the modern era such as Floyd Mayweather, will end their careers with 1/4 -1/3 the contests of a Sugar Ray Robinson - is it legitimate to compare them? Yes and no, but if no, it can be great fun. And perhaps from a Pragmatist vantage point that makes it legit. Thanks.
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In sports (especially boxing) fans love to rank the best boxers, players or teams. So when ranking the Greatest Boxers of All-Time -- is it ethical to include boxers you or anyone else (alive) have never seen before (for no footage exists of them - e.g., Harry Greb)? (Provided that you put in as much research as possible - e.g., books, news archives, boxing historians writings.)