Lucci is cool, that"s why he is so popular.
He has a great design, a cool bad guy atitude and an evil smile:D
And I think that bad guys are really popular in animes. Just remember Vegita in dragon ball or Gaara and Itachi from Naruto, not to forget Aizen Sousuke from bleach:D
The fact is that bad guys mostly get a really fancy design and a really cool personality, that is the answer to their popularity.