smiley in the channel below has a good one, but it displays the top winners based on points won. It does show the win/loss data as well, but doesn't sort on it.
Btw, the best method (imo) of sorting by win/loss ratio would be to just divide the wins by the total games, and it sounds like that is what you have. Yes, a 2-0 ratio has a higher rating than a 7-1 ratio. But perhaps that 2-0 ratio will eventually become a 8-0 ratio, so rating the person lower isn't really a good idea, imo. If you don't want people who haven't played much to hold a top score, then put a limit on it... if the player hasn't played at least 10 games, don't display them in the top scores list, for example.