George Sisler: St. Louis Browns (1915-27), Washington Senators (1928), Boston Braves (1928-30)
George Sisler, the greatest player in the history of the St. Louis Browns, came up as a pitcher, but like Babe Ruth, was too good as a hitter to stay out of the everyday lineup. He was a graceful and complete first baseman, and hit .340 lifetime.
He had six seasons with more than 200 hits, 2,812 hits in his 15-year career, and his 257 hits in 1920 was the best single-season mark until surpassed by Ichiro Suzuki 84 years later but only in a longer 164 game season. He hit just 102 homers, but had 164 triples and 425 doubles. He was MVP in 1922, when he batted .420. Also had 375 stolen bases.
You can see the list of the other firstbasemen at: