I watched 4, 5, 6 and then 1, 2, 3 and then 7.
Most Helpful Guy
The story as constructed by George Lucas tells the story of the fall and redemption of Aniken Skywalker as told from the perspective of his son.
There is another way to watch the films that has is an interesting dramatic experience. Treat the story as the story of Luke Skywalker. Do so by viewing the movies in the following order:
4, 5, 2, 3, 6
(Note that this progression omits episode 1 as this portion of the story only looks at the time of Aniken's youth. It is cannon, but then so is the Star Wars Holiday Special and you don't see anybody talking about that.)
This progression treats episodes 2 & 3 as a flashback that occurs when Luke learns that Darth Vader is his father. The story drops back to when Aniken was the same age as Luke and explains how Lord Vader came to exist. The resolution of the plot arc occurs in episode 6 when Luke Kills Emperor Palpatine with the aid of his father. The resulting death of Lord Vader under these circumstances restores balance to the FORCE and restores Aniken to his revered place alongside other fallen Jedi Knights.