I feel a good player has to be good all around. Even some of the MLG guys that Ive watched and played with arent really that great. The main things that make a person good at CoD are reaction time and accuracy. If you have a good reaction time and good accuracy then you will trump everyone else, despite your playstyle or preferred gamemodes.
I have an above average reaction time. I was told so by a professional scientist after I aced a test that was designed for the reaction times of humans. My accuracy is slightly above average but things like lag and bad hit detection will throw both of these key figures out of wack.
KDR doesnt really matter because of lag though. Some people dont experience lag so their KDRs will naturally be higher than people like me who get a lot of lag. My MW3 KDR is sitting at a pathetic 1.56 right now which is my lowest KDR of any CoD to date. Although my goal when playing these games is to NOT use the OP'ed weapons, hence why I only have under 500 kills with the ACR, less than 50 kills with the FMG9, less than 60 kills with the Striker, etc. The MP7 was my "go to gun" when it came to overcoming try hards and lag and I have 2502 kills with that gun and its my third highest in kills.
Im confident that I could play on a pro circuit level because Ive been known to outwit people and I feel Im tactically superior. My KDR might be crappy but thats because I have extensive lag and I use underpowered weapons. I also rush and I capture flags as much as possible. Im a team player, I play for the win. I gotta pee now so Im just gonna stop now.