That's not an explanation, just a symptom of the problem.

This is what I was trying to convey when I said it might be another example of the problem.

I think it's reasonable, in many contexts, to say that achieving 75% of the highest possible score on an exam should earn you what most people think of as a C grade (that is, good enough to proceed with the next part of your education, but not good enough to be competitive).

I would say that games are different. There is not, as far as I know, a quantitative rubric for scoring a game. A 6/10 rating on a game does not indicate that the game meets 60% of the requirements for a perfect game. It really just means that it's similar in quality to other games that have received the same score, and usually a 6/10 game is pretty lousy. I found a histogram of scores on metacritic:

http://www.giantbomb.com/profile/dry_carton/blog/metacritic-score-distribution-graphs/82409/

The peak of the distributions seems to be around 80%, while I'd eyeball the median to be around 70-75%. There is a long tail of bad games. You may be right that this distribution does, in some sense, reflect the actual distribution of game quality. My complaint is that this scoring system is good at resolving bad games from truly awful games from comically terrible games, but it is bad at resolving a good game from a mediocre game.

What I think it should be is a percentile-based score, like Lumifer describes:

Consider this example: I come up to you and ask "So, how was the movie?". You answer "I give it a 6 out of 10". Fine. I have some vague idea of what you mean. Now we wave a magic wand and bifurcate reality.

In branch 1 you then add "The distribution of my ratings follows the distribution of movie quality, savvy?" and let's say I'm sufficiently statistically savvy to understand that. But... does it help me? I don't know the distribution of movie quality. it's probably bell-shaped, maybe, but not quite normal if only because it has to be bounded, I have no idea if its skewed, etc.

In branch 2 you then add "The rating of 6 means I rate the movie to be in the sixth decile". Ah, that's much better. I now know that out of 10 movies that you've seen five were probably worse and three were probably better. That, to me, is a more useful piece of information.

Then again, maybe it's difficult to discern a difference in quality between a 60th percentile game and an 80th percentile game.