Rating ain't so hard if you keep it simple and not too granular (crappy 100 points or %age score is crap. What the hell is the difference between 64 and 64 score? Fcking sht-all). 5=average, so 6=above average, etc. 10 is godly awesome fanboy territory or something, 9 is fcking enjoyable, etc. 1 is absolute crap that even bacteria won't touch as food. See, easy.
To me 5 mediocre, 6 is below average, 7 above average, 8 good, 9 very good, 10 excellent.