My logic is simple:
10: Perfection (and pretty much impossible)
9: Outstanding
8: Very good
7: Good
6: Above average
5: Average
4: Below average
3: Poor
2: Bad
1: Terribad
I think ratings 5 and 6 are sort of redundant.
Is there really that much between ‘good’ and ‘average’?
Also, for what it’s worth, I tend to think of enjoyment in terms of worth of ‘time’ and something which is 5/10 to my mind is ‘debatably not worth time’, before it decends to annoyance.
My rating system then, since I evidently like smelling my own farts:
10) Stunning - leaves an impression and keeps giving even after viewing.
9) Brilliant - throughly entertaining and recommended to all.
8) Great - recommenced with some notable caveats but the enjoyment of the film is largely uninterrupted
7) Good - enjoyable but with notable caveats.
6) Middling - Entertaining in its own way but not something that is easily recommended.
5) OK - not sure worth the time. May please some.
4) Definitely not worth the time. Passive negative thoughts.
3) Mild annoyance (beyond passive negativity).
2) Annoyance.
1) Great annoyance - annoying you long after the film is over.