Well at least in the BigBadRead poll. JK Rowling's creation, Lord Voldemort from the Harry Potter novels, was voted as the favorite literary villain of all time by British schoolchildren.
The BigBadRead poll was conducted by Bloomsbury, had more than 16,000 votes and JK had this to say of the honor:
I am thrilled and honoured beyond words that Lord Voldemort has been voted best villain in the BigBadRead poll.
I am not sure how he would react ot knowing that he had won a Muggles' unpopularity poll. A mixture of pleasure that you recognised his power and menace, coupled with fury at your nerve at mentioning his real name, I think. His author, however, is absolutely delighted.
UPDATE: You can read JK's comments in full here courtsey of MuggleNet.