After Revenge of the Sith, no one -- including the most dedicated Star Wars fans -- clamored for more Anakin Skywalker.
Really, the ending of Return of the Jedi was enough. We saw Darth Vader escape the grasp of the Dark Side, push the Emperor down an inconveniently placed ventilation shaft, and hug it out with his son Luke Skywalker. Not exactly redemption for blowing up Alderaan, but hey, a guy has to start somewhere.
Despite the conclusion, George Lucas insisted on backtracking and charting the evolution of Boy Darth in his prequel films, starting with scrappy podracer Annie Skywalker in The Phantom Menace and ending with the suited Darth Vader, Star Wars' version of the "Million Dollar Man." The Empire had the technology.
You'd think that would be the end of it. But an AFI top-100 villain does not go quietly into the night. Vader will return.