Star Wars: The Force Unleashed: Ultimate Sith Edition focuses on the battle between Sith and Jedi and takes place between Episodes III and IV. You play as Darth Vader's "secret apprentice" with a mission to destroy the Jedi.
This expanded version of The Force Unleashed includes three new levels and is interspersed with very realistic movie style clips.
The long term appeal is questionable, however. It's one of the easiest games in the Star Wars series and won't take you long to complete.