doady: Giving ratings according to a predetermined "average" makes the average meaningless. An average is used to describe an existing set of numbers, not determine what the future set of numbers will be.
50% is no more a valid "average" than 70%. If people reviewed every single game in existence, or if every single game had equal chance of being reviewed, the average might be 50%. But it could also be 40% or 60% or 30%, who knows. But in reality, video games don't have equal chance of being reviewed. That's why you see a lot of high scores from game critics. They mostly review games that most gamer's are likely to be interested in. They don't review games like Secret Agent Barbie or Baby and Me.
For game user ratings too, the "average" is going to be inflated too because people are selective about what games they play. Let's face it: video games are take a lot of time to play, so people will only play games they are most interested in. So there is a selection process even before the game is played. That's why video games on GOG seem to high ratings. If the people reviewing the games were a completely random sample taken from the entire gaming population on Earth, then maybe the scores would be lower.
Sort of, the problem is that nobody uses the lowest scores. The game ratings you see in general are heavily biased towards favorable reviews where you see basically no games under 20% and most over 70%.
It's not wrong, but it indicates that the scoring system is broken as you're assigning meaningless points that are never used.