Jesus Christ it was a struggle to decide whether Dracula should be #1 or #2 for this list. You could argue it forever. Did you know that Dracula has appeared in more films than any other character in movie history? And when you think about all the other vampire characters influenced by Drac (including the extremely creepy Nosferatu) there's no denying that he's the most influential monster ever made.
Scary and sexy at the same time, you can even blame the entire gothic movement on Drac. And certainly Anne Rice wouldn't have been able to glom on to the whole Vampire thing had he not been around. Of course, the fact that he even remotely encouraged Anne Rice to write books is enough to keep him out of the #1 spot if you ask me!
Bela Lugosi is certainly the most famous Dracula, but my favorite has always been Christopher Lee's portrayal in the Hammer films. But perhaps that was mostly because he could act.