>Short Answer: Really, really, really good.
In 1921, Babe Ruth hit .378/.512/.846, good for a 1.359 OPS. He hit 59 home runs, 44 doubles, and 16 triples*. (Shane Victorino led the majors with 13 in 2009). He scored 177 runs and drove in 171. The only possible knock against him was that he was successful at stealing bases in only 17 out of his 30 attempts**. (Ruth was also famously caught stealing to end the 1926 World Series.)
*Was Babe Ruth a speed demon as well?
**No, apparently not.
Fangraphs lists his Runs Above Average (a statistic that is supposed to quantify how many more or less runs a player created when compared to an average player from that season) as 127.1 runs in 1921. How absurdly good was that? 2009’s leader, Albert Pujols, was 69.7 runs above average, 57.4 runs less than the Babe in ’21. If you add second place Joe Mauer’s RAA to Albert Pujols’, the added total is still 2.5 runs short of Ruth, who accumulated his total over less games. Offensively, Babe Ruth was more valuable than both of 2009’s MVPs combined. So, yeah, this Babe Ruth fellow could rake.
In today’s game, a season roughly equivalent to Ruth’s looks like this:
.328/.515/.863, 1.379 OPS, 73 HR, 32 2B, 3 3B, 177 BB, 129 R, 137 RBI, 13-16 SB.
This, of course, is Barry Bond’s 2001 season, which was worth 119 runs above average, and while impressive, it is still 8 runs short of Ruth’s monstrous season. Bonds also fell .978 points short of Ruth’s 1921 “not being an unlikable jerk” average. The 1921 and 2001 seasons had other similarities: new home run records being set, a league wide offensive explosion, ending in the number “1”, and the Yankees losing the World Series.
Anyway, that’s how good Babe Ruth was in 1921. His skill level was akin to taking the skill set of an already hall-of-fame caliber player, juicing him up, and then setting him loose on the league; or it’s likle taking the two best players from 2009 and combining them to form “Aloe Pauer”, who shares a name with a soap brand.