I think instead of a ladder or ranking system, just have a simple stat system: It would show games played, type of game (1v1, 2v2, 3v3, or 4v4), won/loss record, and #of dropped games. This way you would have some idea about how experienced a player is, and how many times he dropped out of games (would indicate connection problems or escaping because the player was losing). This is really all the information anyone needs to determine how good a player really is.