Dont do 1-50
Make it so that only a tenth of a percent can claim to be the best there is.
Lets just be honest here, using true skill in a game is beyond easy, it has already been developed, so all you need to do is make a system that informs the system of wins and losses and your done. Is that really too hard for 343? If it is asking to much for them to make a playlist or two for their dedicated competitive gamers, than I really dont have much hope for the future of the series