The problem is those in the top 5 are usually playing so much that after a month it's next to impossible for them to be caught.
While I agree that the top 5 log a lot of hours, and thus get a lot of points, the skew in points based on the class you play can also affect your rank.
I'll never be able to catch Video as a sniper when I'm playing medic...
He gets 1 point per headshot, while I get 5 points per ubercharge.
Hmmm...I do get 4 points per kill assist as a medic, maybe I should just be healing him while building my ubercharge - the rest of the team is just going to have to find some med packs...