nice thread. good questions.
first off, if you've never played the game (and have no knowledge) then you will get owned by anybody. its the same with all games. until you learn the maps, weapons and tactics you don't have much of a chance. how can you apply your intelligence to make a strategy if you don't know the game. therefore, knowledge would be by far the most important thing when for a beginner but subsides after you get about 10-20 hours. honestly, instead of knowledge i would write experience. basically how many hours you have played. 1500 hours vs. 200 hours. if this were the case then i would rate them as follows:
1) skill: i'm a pretty smart guy (please don't flame me for saying this...i just am). graduated ivy league with honors. great chess player. high iq. analytic mind...etc. however, i have never mastered the art of dominating other players online. basically i was not born with the amazing hand-eye coordination that others possess. never been able to master the c4 jump throw or the prone jump...blah...blah...blah. Another factor in this is reaction time. i always feel a split second slower than the great players. overall, in my online gaming experience the best i've ever been at shooters is maybe a little bit above average.
2) intelligence: since i'm a smart guy, i play the game to my strengths. i use armor. i have learned how to command well: spot where i need to, drop supplies in the right place, will single handedly defend my team's base with c4 and maybe armor if its available (and by the way there is not nearly enough in the command ability to make use of a smart commander). i know where/what to spawn. i have learned to make use of the minimap and main map to be aware of everything going on. however, with all of these i would rather have deadly aim than the strategic side.
3) knowledge/experience (distant third): i think that while the learning curve is steep, after about 200 hours you aren't going to get much better. all things being equal the more experienced player will win but overall it doesn't make that much of a difference.