Yes, the complexity of character makes it far more fascinating to watch. The wonderful thing about Dark Shadows was that most of the characters were so human, even the supernatural creatures. Many shows today don't have nearly the amount of layers the characters on DS had. Dark Shadows had many of its villains being tragic figures-tortured souls, who have been "forced" to do wrong. Someone who you can relate to or sympathize with on some level. It doesn't work if the villian is pure evil.
Barnabas, for instance, was a tragic vampire. He hated what he was and longed to be free. Viewers felt sorry for him, even though he had done such horrible deeds. You could still see there was a hidden layer of human feelings within him.
Angelique had many human emotions, which caused most of her problems. Nicholas saw how human she was and knew that she would never be a powerful witch like him. (Even though he later let those same emotions get to him) I have always felt sorry for Angelique because I believe she once was a good person, but has been hurt and rejected so many times that she has learned not to trust or care for people. Once again, the complexity of character.
-Lindsey