I'm quite generous with ratings and will happily give out a five-star review on the basis that a) star ratings really don't matter, and b) five stars doesn't indicate 'perfection' as some would have it, but anything above the 80th percentile, ie one fifth of everything in its category (assuming an even distribution).
On the restaurant guide I worked on, the rating system would change according to the whim of each new editor. The one immediately before my time gave scores out of 20, with nothing scoring lower than 10, on the basis that this was entry level (ie 'good enough for inclusion in the guide'), and nothing over 16, on the basis that there's always room for improvement. So in truth it was a six-point scale.
The editor during my time had a five-point scale, with 1 representing entry level, and the vast majority of restaurants featured scored 1 or 2. They had to be seriously good to even get a 3. One year, there was only one 5/5 and I don't think there were ever more than half a dozen. Many restaurant proprietors complained about only getting 1/5, but we had to point out that merely being included in the guide automatically put them in the top ~600 (iirc) restaurants in the country. This rarely proved a satisfactory response.
Subjective rating systems are always flawed one way or another.
