I guess for me the classic opening to A New Hope. It's just so iconic, you remember everything, the Stormtroopers boarding the ship, Vader making his entrance, chocking Captain Antilles, need I say more. I think I might choose the opening to Revenge of the Sith as my second favourite as it felt like the first time a prequel felt like a Star Wars movie despite immediately going back to bad romance. After that I would choose Empire, Jedi & Force Awakens though not necessarily in that order. I can't really decide which order to put them in. They would be followed by Rogue One and then both Phantom Menace & Attack of the Clones though I can't decide which I prefer more, but does it really matter.