(from a discussion on RPG Haven)
Game design is engineering, not art.
I'm not putting a "higher" value on "art" here - that is, I don't think art is just the stuff you find in museums. I do put a value on any word. I'm a professional writer - I make a good living putting words together - and words have value. Anyway, art, any art, is an expression of the artist. The work completed is sufficient unto itself. If no one is there to hear it, that particular tree still can be heard falling, because the hearer - if there is one - doesn't matter. Games are not sufficient unto themselves. They are tools to give others the means to produce enjoyment. Treating games as art is wrong - not morally or ethically, but in the sense of it being bad for games and gaming.
I think that the reason why game design reminds you more of art than engineering is the subjective aesthetic component one brings to the game. There are a lot of valid styles of game, just as there are many valid styles of art. The discrimination - why one like this game or this piece of art instead of that - is subjective. In engineering, one can point to objective performance as criteria for discrimination.
The thing is, there are objective criteria for games too. The games must work, just as a bridge or a truck must work. The problem for judging games on objective performance is that the performance bar is very low. In other words it's easy to design a functional game. So we turn to secondary, aesthetic discrimination. Like a bridge, a game can aspire to beauty as well as functionality, and standards of beauty are notoriously subjective. But even a beautiful bridge is no good if it can't perform the fundamental job of a bridge, which is to carry traffic from point A to point B above difficulty C. An artwork in the shape of a bridge may have aesthetic appeal and merit, but it isn't a bridge. Art can only be judged by aesthetic criteria.
Thus the first and foremost duty of a game designer is to put together a working package of tools which enable others to produce whatever they wish to produce, be that art, fun, or anything in between. This is why I think it is much like software engineering. There is a high aesthetic - and therefore subjective - component in finding a program that does what you want the way you like it done. One person's bells and whistles are another person's lead weights, just as one person's intriguing fiddly bits are another person's absurd minutia. Yet software engineering, like game design, is an engineering discipline, not art.