There is, of course, a formula to Disney films. There's the hero or heroine, the love interest, the talking-animal sidekick(s), the incompetent henchman, and of course, the threatening but not-too-threatening-to-scare-the-small-children-silly villain. Often, the quality of the villain directly relates to the quality of the Disney classic. This list may very well be a sneak-preview of a forthcoming Top 5 Disney Animated Classics. (I have to re-watch Mulan first.)
5. Hades - Hercules (James Woods) - Sufficiently evil, sufficiently menacing, but also probably the funniest Disney villain.
4. Jafar - Aladdin (Jonathan Freeman) - The guy turns into a giant snake. I had nightmares for weeks. Then, he's an evil genie. Plus, he gets to beat up Gilbert Gottfried. For the win.
3. Ursula - The Little Mermaid (Pat Carrol) - God, she's creepy when she makes sexual innuendos. "Poor Unfortunate Souls" is one of the best songs in the whole Disney Renaissance.
2. Gaston - Beauty and the Beast (Richard White) - The trick about Gaston is that for most of the movie he's portrayed as a harmless buffoon. Just when you're most at ease with him, they hit you with "Kill the Beast". From that point on, he's one of the darkest villains in the Disney Canon.
1. Scar - The Lion King (Jeremy Irons) - For one thing, Jeremy Irons has one of the best "evil" voices in animation. (His biggest competition is Michael Ironside (no relation), the voice of Darkseid in the DC Animated Universe.) He's a killer, he's got that scar so you know he's evil, he's got that sarcastic wit. "Be Prepared" kicks ass. And let's not forget the single most badass line in the Disney canon: "Long live the king." Amen to that.