Wow, seven pages of comments and no one mentioned the new Cylons (toasters and skinjobs).
Also, most of the villains here are Game, Anime or comic book it seems. Not a HUGE amount of movie villains but you gotta give it to the Gruber Brothers. I know someone mentioned Hans but Simon was so much meaner to John McClane. Hans just wanted him dead. Simon was just screwing with him for fun.
I've only seen one mention of Buffy villains. How about Glory/Glorificus/The Beast? How could you hate her? She was just too adorable in her incredible self-centered, whiny ways. Plus she was incredibly hot.
The Assassin from Serenity. Nothing but death that guy.
And lastly, Bucho from Desperado. "Look over there. Who's that? I've never seen him before. *BANG* See? How hard was that?" Priceless