Check out Elo Rating System, Jan: https://www.wikiwand.com/en/Elo_rating_system. It details methods to rate players of a competitive game in to higher/lower rank buckets, based on their skill levels. It all started with chess. A lot of online competitive games now-a-days use this sort of rating, to rank their players.
Alternatively you can also look into this: evanmiller.org/how-not-to-sort-by-average-rating.…. Evan details a way to correctly sort a product according to user ratings, using statistical sampling; and does it "correctly" even in the case when the no. of ratings between two products are disparately different. You can adapt this model for rating your players; where the no. of ratings would be analogous to the number of games played, and a positive rating is a win, a negative one, a loss.