I believe the problem is that reviewers have been raising the bar in terms of ratings.
I mean, even 6 years ago, games that were rated between 7 - 8 were deemed as good games. Where as anything higher was fairly superb. It also deals with how gaming companies set the bar in terms of good games too, imo.
I think it's the problem of the growing gaming industry. Publishers are becoming much more invested in what they're sinking money into, and so a lot of them are imposing this insane guideline that a game's metacritic score has to be in the 80s or higher, or 8+ in 10 point scores. That mentality spilled over onto fledgling gamers because the communities were opening up more, too, and so you have the people with the money on both ends (publisher and consumer) with skewed ideas about scoring :/