When games are good, they can be very good. They can influence your views on the world, change your ideals, and even guide the course of your life (like good old FFVII, who not only inspired me to write, but gave me my alias too). Good games at their best are not just something to play, their art!
When games go bad, however, they can be nothing short of psychological torture. If something that's supposed to be fun suddenly becomes painful, boring, or worse; work, then that game has failed in it's main objective: to be entertaining.