The '73 Mets had the most amazing season I've seen: finished 3 games over .500; slogged upward in the second half of the season, with Tug McGraw screaming "You gotta believe!!!" after every win; beat the Big (Bad) Red Machine in the NLCS. Lost to the great '70s Oakland team in 7 games.
The lists would probably have to be separated into pre-1920 and post-1920 teams.
'73 Mets team ERA: 3.26 (3rd in NL) Team Ks: 1027 (1st in NL). Seaver pitched 290 innings, 251 strikeouts.