There's a few ways of looking at this. I personally don't think that a 10 makes a game perfect but it does indicate that it's a great game. A classic. The thing is if you have a 1-10 rating scale but never award 10s because of a pre-conceived notion that no game is ever worthy then essentially you have a 1-9 scale. I think that my pet peeve with ratings is that there's generally not enough 2-5s even though I feel that there are certainly games that deserve them.