Art is a step forward, an ambition. It looks at what humanity as a whole – not just individual pockets of it, or even specific individuals, but all of it – can do, and seeks to find out if this really is all there is to it. is the present the limit case of human capability, or can it be pushed further, through intuition, invention or iteration? Are we to settle for what happens to exist – a contingent category if there ever was one – or can we, humanity, move things forward? Art is an endeavor that requires craftmanship, but which can not be reduced to it. There is always a step of transgression, transcendence, transubstantiation. In order to do art, you have to look at a map that says “you are here”, and respond with a forceful “fuck that, let’s get a move on”
To return to your original question, “do computer games have to be fun”, I say, it misses the point. The question is not even wrong. You are thinking too small. We can do better than that. Let’s get a move on