What makes the prequel interesting is that you can watch them in either order really. Obviously, most people saw the movies in the order of 4, 5, 6, 1, 2, and 3. And it is obvious that the prequel are designed this way, hence all the nods to the original trilogy. The movies are made with the expectation that you've seen the original trilogy. However, a newer inductee into the Star Wars world might view the films in the 1-6 order, which would ruin the surprise at the end of Empire that Vader is Luke's father, but it would also make Anakin's downfall to Vader at the end of Revenge of the Sith more surprising. Remember, we all went into the prequels knowing that Anakin eventually became Darth Vader, but a newer fan who was inducted with the prequels would not. So the intrigue and surprise would be there, but in a different way depending on which order you saw the films. Something else worth considering is the younger fans of the Clone Wars series who haven't seen any of the films, what kind of surprise might they be in to learn what happens to their hero Anakin who is, as such, portrayed much more heroicly in the Clone Wars series. All in all, I doesn't really matter what order you watch the story in, be it original, prequel, series...prequel, series, original...or series, prequel, original...you're going to get a different set of surprises that work work in a different way.