I think your last paragraph, Stol, applies to MMO's too. I learned alot when playing, including coordinating in a party atmosphere, and it was mentally stimulated to perceive the patterns inherent in the game and develop strategies to exploit them.

But the first part holds...The whole point is to keep you playing. But for me, I eventually got bored; doing raid after raid (or mission after mission) to achieve items that just let me do more raids and missions got old.