My killrate is at a 2.85 right now (599Kills/210 Deaths). Used to be at like a 3.09, but I screwed up my last few matches which brought me down. Then again, my accuracy is horrible with 17% on MP40 which is what I use most of the time. If you want kills, the best I believe is FFA. FFA is good for kills because 75% of the time, there will be someone around the corner. I don't think Kill Rates really matter depending on the game mode you play. For example, if it was Domination, I'd rather have someone who captured flagpoints than someone who just went around killing.
Being a top killer doesn't mean much. I've seen my share, where one team had a very good player that had like 35-5, while the rest of the players on his team were in the negatives (16-15, 10-17, 5-19). And the other team, most of them were hitting neutral (16-15, 15-15, 14-15), were winning. It just goes to show that teamwork means everything and you can't always go for kills all the time (in objective-based games like Headquarters).