Ruth, Mays and Aaron all played for two different teams in respective cities: Ruth for the Boston Red Sox and Braves (bookending his years with the Yankees), Mays the NY Giants and Mets, and Aaron the Milwaukee Braves and Brewers (this in addition to being the only members of the 600-homer club (so far)).

it should be noted that Ruth was regularly hitting 50 in the '20s when no one else came close to it. nowadays Brady frappin' Anderson hits 50!
-ron obscurity