production, paints the most complete picture of how a hitter dominates his era. Calculated by adding a player's on-base percentage (the sum of hits, walks and hit-by-pitches divided by the sum of at bats, walks and hit-by-pitches) and slugging average (total bases divided by at bats), OPS weighs batting for average and slugging, but also factors in walks.

When we go a step further and calculate a hitter's rating in relation to the league norm or average, we call it OPS+. Not only is OPS+ determined by a hitter's achievement relative to the league average, it also includes his "park factor," which slightly raises or lowers his rating based on whether he played in a home park favorable or unfavorable to hitting. The league average for hitting in anygiven year is set at a constant of 100, so a player with an OPS+ of 200 is twice as productive as the league average, while a player posting an OPS+ of 50 is performing at only half the norm. Of more than 15,000 major league players since 1871, just one has doubled the league average for his career: Babe Ruth finished his career with an OPS+ of 207. In this article, we look at the players with the best career OPS+ ratings of all time and use them to compile a list of the greatest hitters of all time.

1. Babe Ruth OPS+207
Since Babe Ruth's retirement in 1935, many of his offensive records -- such as home runs, runs scored and walks -- have been surpassed by players