I think people get hung up on thinking that 7/10 is average, and also the opposite end where people get hung up on thinking that 5/10 is the LITERAL average. 7/10 is the "average score" because, if you take all the scores that have been assigned, that's what they average out to be. 5 is the numerical average, but that doesn't really have anything to do with what the perception of the "average video game" is. The "average video game" is a 7/10 because that's what video games end up being, on average. Most video games are pretty good on average. There are fewer games that are a literal 5 out of 10 "average" experience. Hopefully I'm making sense with that explanation.