the ranking system on halo 3 was so very well made and competitive
When other big title games came out i would play them for maybe a week or two then return to Halo
I could play all day on weekends without even thinking about it (10 hours+ a day)
I played Halo Reach for a few days... then dropped it
Call of Duty multiplayer style (where the more you play the higher your rank) isn't my preference)
It isn't as fun as skill-based "trueskill" system that we all (competitive players) love