The article is right in saying that a game's goodness exists outside the mind of the players. But by saying it only exists in the mind of the game developers is moving it from one group of people to another.
Plato would argue that a game's goodness exists by itself, not in the subjective mind of the players or game developers.
A good game is one that is unified, proportional and whole - based on the sum of its parts.
Great graphics but no gameplay.
Great story but short length.
Great music but bad sound effects.
A good game is proportional, unified, and whole and it doesn't matter what the game developers declare it to be a great game.
So begins the circular logic.
A: The "goodness" of a game is independent of subjective perception.
B: The "goodness" of a game is based on is proportionality.
C: The "proportionality" of a game is based on subjective assessment of its observable parts.
D: The "goodness" of a game is therefore based on subjective assessment of its observable parts.
E: The "goodness" of a game is NOT independent of subjective perception.
After all, who defines "great graphics?" Or the even more nebulous "gameplay?" What IS a "great story," or an appropriate length? And then you mention "great music"--right, there's a topic everyone has agreed upon easily throughout the ages. It's all subjective, and Plato knew full well the hard reality that experience is always subjective, truth is objective, and so any attempt to ascertain the truth is only an attempt.
We've established there are two extremes:
1) "Hardcore gamers": This extreme thinks games should be tailored toward the elite. It should be difficult to master, and the enjoyment comes from the sense of accomplishment when they are mastered. Games that scale down the difficulty are just contributing to the erosion of the challenge (and thus the accomplishment).
2) "Casual gamers": This extreme thinks games should be tailored toward easily-accessible fun. The challenge is just there to help the game pass the time, or to provide goals that can be reached with time more than effort. Games that are too difficult or time-consuming are just narrowing the gaming market toward people with a lot of free time and disposable income.
Neither extreme is wrong, nor is either completely right. As with most things, the correct answer exists on a continuum BETWEEN the two. Games that are accessible enough that you're still building the next generation of gamers by providing new experiences that build requisite skills (and interest)... but are also challenging and innovative enough that the field of game design is moving FORWARD as both an art and craft.
Interestingly, but not unexpectedly, the hardcore gamers are the far more uncompromising of the two. Casual gamers will gladly play "hardcore" games in 'carebear mode,' but a great many hardcore gamers are vocal about their hatred of a game that even includes a 'carebear mode' of any sort.
I was pretty disappointed with this article. I hate the idea that philosophy is something that some hairy men made out of marble did in Ancient Greece. "What makes a game good?" is an interesting philosophical question, and I don't think asking "What would Plato say?" is a good way of answering it.
Speculating on the application of Platonic philosophy to game design is a perfectly valid thing to do, but it's a much less general question than addressing how the idea of 'goodness' applies to video games. It seems like the sort of thing that's probably only really interesting to philosophers, and even then of a particular bent. Why would you care if you didn't have an interest in Plato in the first place?
My real bones with this article is that it's reinforcing a negative image philosophy of being about beardy old Greeks and -ism's, rather than dealing with the really interesting issue and showing that philosophy is interesting and relevant.
(and yeah, I am a philosophy student)