Star Wars IV: A New Hope
This one has almost everything with a familiar hero story. At the end of the two hours it's fun, exciting, and shows you intriguing new worlds that you walk away from--even as an adult--thinking you have just seen intriguing new worlds.

Star Wars V: The Empire Strikes Back
Finally, the truth can be told: heroes have bad days, too. They get themselves into messes, their enemies get them in messes, they don't get themselves out...or do they? Wait for

Star Wars VI: Return of the Jedi
This one DOES have everything: romance, music, comedy, drama, adventure, horror. Anakin saves Luke, Luke saves Anakin, Han and Leia stop playing it cool and express their love.

Star Wars I: The Phantom Menace
Yeah, people will disagree with this one. However, we see a galaxy without war. One that hasn't known war for a long time. Sure, there are still injustices, but it gives us a chance to see the galaxy at peace (in the beginning) and through the eyes of a child (something we only get once in the GFFA).