Singleplayer games are power fantasies: you as hero, rescuing the world from certain destruction. Multiplayer games are all about balance. Valve spent years making Team Fortress 2 a balanced experience for two teams and nine classes. They succeeded. They should be proud. They shouldn't have bothered.
It's the inherent unfairness of life that makes it so exciting. Sometimes you're up, sometimes you're down, but it's always interesting. More multiplayer games ought to be fantasies about a lack of power.