I have recently discovered that a positive KDR and win/loss ratio generally means the player is much better than average. Never thought about it until I started paying attention to the stats of the people I was playing with. I generally play with some guys from e46fanatics.com now and most of them are positive on both stats. It's a world of difference compared to playing with random peeps or players who aren't as good.
That said, a player who doesn't play with other decent or good players will have a much harder time getting a positive kdr and win/loss ratio on most game modes. If your team sucks, it will make it much harder for you to do well in the game.
I agree 100%. I usually will not play unless I have at least three other guys I know own my team.