Absolutely DRACULA (1931). As has been said, Lugosi *IS* The Count. He defined the character in a way to which ALL others are compared.
Also like all of Christopher Lee's portrayals. Good stuff.
One I have not seen mentioned here yet is FRIGHT NIGHT (1985).
Really, there are too many good ones. Even in the totally bad B realm...POLISH VAMPIRE IN BURBANK will always hold a special place...just because.
I like Leslie Rice's video review style, and he offers a fun one with his Top Ten Vampires list.
http://blip.tv/terror-obscura/terror-obscura-top-10-vampires-5838268