For so many growing up in the 80s and 90s, the last duel between Luke and Vader served as an archetype for the ultimate showdown between good and evil. It remains watchable even the hundredth time around. Plus it was the first time we were shown the true evil hiding in the shadows behind Vader. The cackling Emperor goads Luke to either kill him for revenge so he can rule the galaxy with Vader, or kill Vader so he can take his place. As is the same with all the greatest lightsaber battles, it's what is happening beneath the surface between the characters, and not the stunt choreography, that made it riveting.