The Good:
Ian McKellen's Magneto is pretty spot-on, as far as I'm concerned.
I like Hackman's Luthor a lot. He's hilarious, first and foremost. Brilliantly acted. Quotable, oh so quotable. I never realized that the trio of Luthor, Teschmacher, and Otis can be seen as the evil counterpart to the Superman, Lois, and Jimmy trio, until I recently saw it pointed out in the "It's really that good" review. Obvious, in hindsight, I know, I know. Anyway, that adds another layer to it. I have little interest in comparison to the comics, which I was familiar with when I first saw the film, by the way, both in Superman and Superboy stories. That said, arguably a better and more interesting version of Luthor is the one in the animated series that looks like Telly Savalas and is voiced by Clancy Brown, but that's off-topic.
Heath Ledger's Joker is good. Julie Newmar's Catwoman, too. Burgess Meredith's Penguin is pretty definitive for me. Frank Gorshin's Riddler is always goofy fun. I enjoyed Tom Hardy's Bane and Cillian Murphy's Scarecrow, too.
I liked Doc Ock in Raimi's Spider-Man 2 for two reasons. Alfred Molina was very good, and the visual realization was astonishingly vivid, especially for the time.
Tom Hiddleston's Loki is top drawer.
The Bad:
Danny Devito's Penguin. Sorry, Danny, I really love you in other things, but not this. The disgusting elements of this character, the Tim Burton-isms to coin a term, they really turned me off so much that watching this film was at every point pretty much no fun at all. I do not care to see this film ever again.
Yup, smoke-cloud Galactus in the Silver Surfer film was a big waste of time.
I had a similar reaction to the yellow-smoke Parallax in Green Lantern. It's irrelevant how true to the comics it was; as a film villain, a bunch of yellow smoke that could either posses you or bring a tidal wave of destruction was ridiculous; what are effectively forces of nature do not good villains make in film, generally. Too bad they wasted Sinestro by presuming that they could earn a sequel, because he was one of the bright spots of that train wreck.
Also bad: Willem Dafoe's Green Goblin, because his mask hid his face for so much of the time.
I never cared for Cesar Romero's Joker. I can't really put my finger on why exactly, but the voice was always ridiculous, never threatening, and I can never unsee his mustache!