well, not all which are in the toplist has gotten a good skill, some of them just have the skill to click the left mouse button (fops with arty)
many do rating with fops and cops,
skill means how many hs you can make so if you know some1 who is maybe low+ then play a 1o1 e.g. on valhalla on an etpro server and check who is better, if you make then many hs and kill him more than he does then you're probably med-