My thinking for this is that someone has to be inner circle Hall of Fame talent-wise and also be an important part when telling the story of baseball. Ruth and Mays obviously qualify. Satchel Paige was the most famous baseball player in the country in the 40s (with the possible exception of DiMaggio) and had the talent to match. Robinson may have been the most historically significant player, but couldn't touch Aaron on the field. What Aaron dealt with when breaking Ruth's record is second to Robinson in the story of black players in the majors.