In horror the baddies are monsters even if in human form. In adventure, whether fantasy, science fiction or superheroes, they are opponents. In comedy they are naughty clowns. Regardless of their genre, however, the villains are characters against the protagonists.
As a writer, artist and game designer I love villains. They are usually the characters I create first. More often than not my heroes are afterthoughts to make the baddies more interesting.
I believe in freedom and justice. I want the villains to lose. I want the heroes to win. I want their struggle sexy, thrilling and grimly amusing. I want to care because I care about the heroes and villains alike. Yes, I want my baddies defeated... but I must love them to enjoy the experience.
A villain may be hateful or greedy or simply obsessed with a notion. Regardless, it would be bad for the villain to prevail. The villain must be thwarted or at least duly punished. Yes, a baddie may ultimately win but the triumph of evil is uninspiring.
Winning does nothing to make villains interesting. A memorable look and eccentric quirks given a catchy name does the trick; for bosses, underlings and lone baddies alike. Yes, depth can make a villain endearing but such is unnecessary to make one interesting.
Villains are my favorite characters but not because I am cheering for them. I want my masterminds clever only to be bested by witless courage. I want my brutes and killers outfought by indomitable weaklings. I want my nameless throngs easily and readily slaughtered by lone heroes. I love my baddies for being sexy, thrilling and grimly amusing. Yes, even my ugly villains are sexy because villainy is a spicy flavor.