Luke Skywalker Story
IV: A New Hope
V: Empire Strikes Back
Anakin Skywalker Story
II: Attack of the Clones
III: Revenge of the Sith
Combined Story:
VI: Return of the Jedi
Episode 1 should be skipped because it doesn't add much value to the stories and it has Jar Jar Binks extensively. (Although check out the first 3-4 minutes of the movie because the Jedi fight scene is awesome. Just turn it off when Jar Jar appears.)