Currently, each participant in a league is ranked by score. A player's score is found using this equation:
Score = Losses + (2 * Wins) + Bonus
So a player's score goes up by 1 for each loss they have, and by 2 for each win they have. The 'Bonus' value is less self explanatory. Your bonus value is equal to the number of matches won by players you have beaten. Thus, each win gives the same base increase to score, but beating someone who is doing well in the league increases your bonus score by a lot more than beating someone with fewer wins.
This methodology may be tweaked for future leagues, depending on how well it serves the needs of this community.