(Warning: big villain fan here!) I don't "perfer" any of these types per se, because I'm a fan of almost every type of villain. But they have to be done exceptionally well.
Harmless Villains have to be treated as such and actually be funny for them to work. Good examples would be Dr Drakken, Dr Doofenshmirtz, Excel and Hyatt, The Monarch, The Ameoba Boys, Prince Eccentro, and Dr Light. The worst kind would be like Team Rocket, who show up in every single episode yet never provide any real conflict. And thus they stop being funny. :yawn:
Ineffectual Sympathetic Villains are a step-up in terms of doing harm and evil but they're usually always failures, which is what earns them something resembling sympathy from us. This is what the likes of Team Rocket, Jack Spicer, and Emperor Pilaf used to be before they became harmless. Examples would be Plankton, Invader Zim, or Duke Igthorn.
Anti Villains are the bad guys with heroic or virtuous traits and sympathetic motives. These are particularly in need of good writing in order to make us feel for them. The classic examples are Mr Freeze and Magneto, but there's also Long John Silver, Prince Zuko, Terra, Pinky and the Brain, and Gargoyle's Macbeth.
Magnificent Bastards are the very intelligent, ruthless, self-serving and above all stylish villains who know exactly how to get what they want. And they usually do. Examples would be Lelouch Lamperogue, Light Yagami, Vegeta, Sir Crocodile, Sosuke Aizen, Xellos Metallium, Lex Luthor, The Joker, Doctor Doom, Megabyte, Megatron, Princess Azula, Nerissa, Green Goblin, Vlad Masters, and of coure David Xanatos. Basically, Magnificent Bastards are some of the most dangerous villains. :evil:
A Smug Snake (Magnificent Bastard wannabe) can also be manipulative and just as enjoyable, like Orochimaru, Katsuhiko Jinnai, Slade, Admiral Zhao, Prince Phobos, and Lord Cedric. If a Smug Snake is written to be way more of a threat than he/she should be, however, you're likely to just get annoyed with them. :shrug:
And Complete Monsters are the pure evil villains that we just flat out hate. Through mercilessly evil actions and zero redeeming qualities, they're the kinds of villains we're rarely able to enjoy but can at least appreciate. These villains are the likes of Johan Leibert, Freeza, Elder Toguro, Arlong, Gendo Ikari, Firelord Ozai, and Judge Frollo.
All others are usually Card Carrying Villains and Big Bads. And they have their evil merits too.
I agree fully on this viewpoint, but I think you may have mistyped that one part about Hannibal Lecter. Didn't you mean
"wasn't?"
Couldn't have said it better myself. Who was the bonehead who decided that Carnage should become such a recurring villain, anyway?