Obv such a list is going to depend heavily on your definition of "Dominance". As with MVP, people's interpretations or ways they measure it will differ. This is how ESPN measured it:
Quote:
Methodology
We used our unpatented five-step process to determine the most dominant athletes of the past 20 years. First we looked at the top league in every sport that has global annual revenues of $100 million or more and for which there are reliable annual overall rankings or ratings of individual athletes for all or most of the past 20 years. Then we rated those sports' athletes in each of the past 20 regular seasons by the best single performance metric available, adjusted these ratings to normalize athletes' scores in each sport across time, narrowed our focus to the top four athletes each year in every sport, then adjusted the data again to put these players, across sports, on a common baseline. Then we added up the results to achieve this list, in which one "dominance share" equals one standard deviation of performance by an athlete beyond the top four players in his or her sport for one season.
Metrics
MLB: Wins above replacement (WAR), according to FanGraphs; NBA: Value above replacement player (VORP), according to Basketball-Reference.com; NFL: Defense-adjusted yards above replacement (DYAR), according to Football Outsiders; NHL: Goals vs. threshold (GVT), according to Hockey Prospectus; WNBA: Win shares, according to Basketball-Reference.com; ATP, Formula One, WTA: Tour or championship points; LPGA, NASCAR, PGA: Prize earnings; FIFA, International Cricket Council, World Rugby: Player of the year voting; Boxing, MMA: ESPN, The Ring and FightMatrix pound-for-pound rankings; Olympic track and field: Track & Field News rankings
Cliffs: They basically just compared WAR, VORP, DYAR, etc, made some bad adjustments, and
voila...bad list!
Sidenote: They didn't even measure the NBA and the WNBA using the same metric, lol.