I play games mostly for the story and the fun involved. If a game is too easy I don't mind, I'll still complete it though depending on the type of game, the nature of it may too repetitive for me to bother touching it again once I've completed it. Other games however, I can enjoy no matter how easy I find them, simply because I enjoy the game or it's story or it's world so much. Games like Final Fantasy often fall in to this.

I find it's far more aggravating to find a game too hard to enjoy. I completed Call Of Duty 4 on Veteran difficulty for example, but many of the levels felt very grindy, it was advancing 10 feet, dying, being pushed back 5 feet and then trying again until eventually you memorized exactly how enemies would react to your tactics and where they would be to take down. I enjoyed it but I'll forever have 980 Gamer Score on that because smurf the mile high club achievement, that level is way too difficult for just 20 gamer score. That said, when playing an FPS game, I generally want the higher difficulty so it is a challenge, though the challenge should be fun and not just a case of slowly forcing my way forwards in a war of attrition.