Depends really. If special effects and big battles aren't a problem for you and you love story to move in one direction, watch them in order from ep 1 to 6. However, if special effects are a problem and you dont care about going in order than 4-6 first then 1-3. I liked to watch them 1 to 6 but my brother did that with me and didn't like it because after all the big cool battles in 1-3, 4-6 felt weird special effects taken into account. Plus the battles weren't that great to be honest. All in all the danger stems from going from the 2005 Ep. 3 RotS to the 1977 Ep.4 A New Hope. There is a giant gap in fighting scenes and special effect quality that Ep. 3 does well and story which Ep.4 does well. So In my opinion a true star wars fan watches them 1, 2, 3, 4, 5, 6 because it emphasizes story above all else. Watching it in reverse order emphasizes special effect quality and action scenes.