A game should be good, but that doesn't necessarily mean fun.
Art isn't always about positive emotions, some of the most captivating art is so involving because it explores the more solemn side of human emotion. Think if movies and books only existed to create happy joyful or visceral emotions. We would have no Schindler's List, no Grave of the Fireflies, no Obasan or Watchmen. Now games are a very different medium then movies books or comics, and how they will explore those themes will be different, but they are places games should go.
A lot of people have named survival horror as a reason for there answer to be no, and I disagree with this logic, at least partially. There is something thrilling and fun about having the shit scared out of you. It's a lot like riding a roller coaster. Stress and fun are conceptually tied together. Stalker I think is a better example of a game that is excellent yet not fun. Stalker is a good example of a game that is both engaging and really... kind of miserable. And going in the complete opposite direction, Journey. Now don't get me wrong, I love the shit out of Journey, what a moving game, but with perhaps the exception of the sand surfing level I don't think I found it fun in the classicle sense of the word. It's a moving game, more solemn then anything. A meditation if you will.