Ratings are purely subjective. However, there is some logic behind the rating according to the form of art:
The rating scale for films has three levels:
The High Arts Review Silver rating means the film is very good.
The High Arts review Gold rating means the film is a masterpiece.
Films that don’t qualify for one of the above ratings belong to the average category (and below).
A star rating system is used for classical music reviews, from a scale from 1 to 5 stars. Since the quality of classical music releases is most of the times higher than that of contemporary films, the rating will most likely aggravate between 4-5 stars. This means that usually only quality recordings will be reviewed.
Book reviews do not have a rating system. Any positive/negative aspects will be discussed thoroughly within the review itself.