Stats are just data points, we ascribe meaning and most have no idea what kind of player they are looking at... stats like KD are not a great indicator of skill - they can be, but it does not follow that a high KD = good player, even in general terms.
I know that in H2 if I saw someone with a hardcore level above 40 the kid either cheated or was very very good. I know that in H3 if I saw a 50 in MLG, he either boosted, or again was very very good. In Reach, once the Arena was changed to wins/losses, if I saw a top 10% Onyx, he was likely very good. Again all in terms of a team game...
I like wins/losses being the determining factor of any reflected skill level in game, and being a factor in matchmaking. It allows for things to be accounted for that directly impact winning and losing that cannot be a stat. Clutch plays, quick thinking, communication, team shot, player sacrifice in objectives, and how a player moves with others. All of which go further in making up a good player in team games than KD.