Great article at Rampant Games about enemy design ideas, check it out at http://rampantgames.com/blog/?p=3665.
I’ve thought about this a lot of times: the villain is as important as a hero (and in my opinion, in a game medium, even more important, since the hero characterization is sometimes taken over by the player). Would Star Wars be the same without Darth Vader?
Don’t have time to go into this, but just thought I should share it! 