I submit that Vader is actually a fairly well written villain just in SW alone. The movie gives you hints at a more complex history of the character, which gives the audience knowledge that there is more to Vader than meets the eye. Obviously we know that he’s powerful with the Force, and is therefore unique among the Empire and all the other bad guys. We know that he’s not entirely aligned with the Empire’s leaders—he only works directly with Tarkin and the Emperor—and would just as soon kill one of the Empire’s people (“I find your lack of faith disturbing”) as he would a rebel. He scoffs at the idea of the Death Star, and aligns himself as more of an agent of the Force. We know from Obi Wan that they were originally friends but eventually turned and “killed” Luke’s father. Just that alone—that he was once good but then turned to evil--makes him incredibly intriguing. They may not spell everything out, since they were leaving much of it for the sequels, but there is more than enough there to paint a strong character. And I’m not alone in thinking that Lucas ruined him by showing way too much of his background in the prequels. He worked much better with the audience filling in the blanks.
So I’d say that is a multi-faceted, layered, complex character right there, and the reason he has persisted as one of the best cinematic villains ever since.
