When I was growing up New York City had three teams: the Giants with Willie Mays as center fielder, the Dodgers with Duke Snider, and the Yankees with Mickey Mantle. Snider got to the majors at 20, but became a regular in 1949 at 22. Mantle got to the majors at 19, becoming a regular in 1952 at 20. Mays got to the majors at 20 and became a regular in the same year, 1951. (His career was interrupted by military service.)
There was debate over who was better. My sister was a Dodger fan, so favored Snider. I was a Yankee fan, so favored Mantle (even had a baseball card for him). No one in the house was a Giant fan, so Mays didn't get equal time.
It seems clear now, on Mays' 90th birthday, that he had the best career and likely was the best player. The link has a good discussions of him.
