I don't know if COD4 is similar to 2142 other than it has team-based game play and a ranking system. I remember playing 2142 a little awhile back but COD4 seems to be an entirely different experience. Though I'm still learning the game/maps, I'm not doing too bad...though I'm only playing FFA at the moment. I generally finish in the top ten if not the top 4 on most maps (the ones I've see so far anyway). It's a badass game!
-dd1sk