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.