The top 25 RBI/G played (games played by the player), minimum 81 games.
Sam Thompson 1894 1.42
Sam Thompson 1895 1.39
Sam Thompson 1897 1.31
Hack Wilson 1930 1.23
Al Simmons 1930 1.20
Cap Anson 1894 1.19 (Cap was 42!)
Hank Greenberg 1937 1.19
Lou Gehrig 1931 1.19
Cap Anson 1886 1.18
Jimmy Foxx 1938 1.17
Hugh Duffy 1894 1.16
Dave Orr 1890 1.16 (Dave is listed as 5'-11", 250 on bbref)
Ed Delahanty 1894 1.15
Babe Ruth 1929 1.14
Lou Gehrig 1930 1.13
Lou Gehrig 1927 1.13
Babe Ruth 1921 1.13
Babe Ruth 1931 1.12
Hardy Richardson 1890 1.12 (he and Orr were in the Players' League)
Manny Ramirez 1999 1.12
Hank Greenberg 1935 1.12
Ed Delahanty 1893 1.11
Joe DiMaggio 1937 1.11
Al Simmons 1929 1.10
Jimmy Foxx 1932 1.10
Note how many of these seasons were from the hitters' eras of the 1890's and 1930's. Even 1999 was a peak year for roidball.