Trash Can: Is a movie so bad it's destined to be either destroyed underfoot or burned. The lowest rating.
Wretched: A movie with no redeeeming factors that's just a hop away from the getting the big Trash Can. Below average: While there might be a few things worth seeing the end result is skippable at best. Average: Passable fare that's decent viewing but isn't very inspiring. Good: An entertaining movie with enough things about it to recommend. Very Good: Entering the top tier be it by either taking risks or simply delivering the "cool". Great: About as close to perfect as you can get but something is holding it back either creatively or in execution. Excellent: The peak of genre movie making.