Tabling the "he played against broke plumbers" angle, Ruth has still got anyone.
Ruth was a flat out better overall batter. Ruth was a flat out better overall slugger. Despite that he wasn't the baserunner Ohtani is, Ruth was more successful at getting on base, at least, anyway. Bottom line, Ruth was the best hitter--
the best, not among the best-- in the league every single season from 1919-1931 except in 1922 & 1925 when he was injured part of those seasons. He was arguably the best in 1918 and 1932, too. Nobody else has ever come close to matching that feat. Greatest hitter of all time.
As great as Ohtani has been this year, at the plate, overall, he is second fiddle to Aaron Judge.
And as for pitching?
In that year, 1916, he was 5th in Wins, 3rd in WAR, 3rd in ERA & ERA+, 3rd in Strikeouts, 2nd in Shutouts, 16th in FIP & WHIP, etc. To put it simply, he was the second best pitcher in the league that year behind only Grover Alexander.
Comparatively, in 2022, his best pitching season, Ohtani was only 4th in Cy Young voting in just the AL. For the league, he was 8th in Wins, 3rd in WAR, 6th in ERA, 5th in ERA+, 6th in Strikeouts, didn't pitch a Shutout, 44th in FIP, 35th in WHIP. I'd guess the baseball hardcores in here
might put him in the Top 5 starting pitchers for that season.