I can answer his question with two points.
1) “The villain makes the hero”, a Hollywood truism. If Darth Vader spent most of his time sniveling about losing his wife and how unfair life is, showing himself as being a neurotic cry-baby who lashes out at others, in a futile effort to diminish his own pain, he would have been just pathetic.
In fact, trying to “humanize” a villain is a terrible directorial mistake and can kill a movie. They should be evil, and like being evil, and know that they are evil, and never apologize for being evil.
2) If you ever want to see a “mundanely evil” Hollywood villain, I would recommend (not really) the movie, Henry: Portrait of a Serial Killer. The actors played it for realism, loosely based on the life of real serial killer, Henry Lee Lucas, and it was so terrifying that it got an ‘X’ rating. And deservedly. Terrifying because it was so entirely ordinary.
It shows the villain as a dull, boring, ordinary person who murders easily, and for a long time gets away with it. Lucas, himself, may have killed as many as 350 people.
Yes, but that doesn’t address the fact that, for the most part, there aren’t truly virtuous heroes that kids can look up to today. Even in Star Wars, you did have Vader, but you also had Skywalker and Kenobi. I would include Han Solo, but he was sort of a self-serving schemer, except for when he redeemed himself at the end.