which is the best multiplayer game in your opinion for pc .

I personally am still a fan of Counter-Srike Source it is everything that a game should have in it which is a solid multiplayer that presents a good challenge. If FPSes aren't what people are taking about than I have to say the second closes would be Starcraft 2 as well the matches that it gets you with players who are good and well some that aren't so good presents its own challenge to the game. That you as a Strategist have to overcome.

Try Entropia Universe. You'll find that it's quite interesting.