In a world which does not accept "average" as acceptable, it occurs to me that I should provide some insight into how I rate films, TV shows, books, etc.
Essentially, I rate the way I grade my students' papers: with an understanding that most things are average, some things are either very good or very bad, and a few things are either wonderful or terrible. Therefore, there is nothing wrong with a 3-star rating.
My rating scale goes something like this:
5 stars - amazing. Blew me away. Stayed up until 2 AM reading/watching/listening to this.
4 stars - very very good. Enjoyed it thoroughly.
3 stars - it was good. I liked it. Maybe it wasn't brilliant, but it sure didn't suck.
2 stars - eh. Something wrong; poor plotting or writing or execution or acting or something.
1 star - I hated it.