1.) The Joker (...of course.)
The Joker is my No.1 because simply, his pure evil nature. The Joker doesn't
have real meaningful reason for all his chaos and murder, he's just a smart but severely "damaged" and insane man who through his unpredictable and sadistic style, is also a very dangerous man. So much so, that he on multiple occasions has caused big problems for the Batman. That's saying something.
2.) Lex Luthor
Lex Luthor is number 2 because I've always liked how much a regular human like him can cause so so much trouble for Superman. He hates Superman soooooo much and is soooooooo jealous of him and his power, that he just can't control himself. True the same goes for many other villains and the heroes they hate, but not all villains can cause as much trouble as Lex. And I can respect that instead of just being the boring type of villain that only sends people out to kill others, he made a special suit dedicated, to putting the hurt on Superman face to face.
3.) Ra's Al Ghul
Ra's Al Ghul is a beast... he is a expert ninja assassin, he's lived for hundreds of years thanks to his "Lazarus Pit", giving him plenty of experience in combat of different forms and who knows what else, he has his loyal "League of Assassins" to do things for him and join him in battle when needed... the list goes on and on what more do you want. In certain versions he's even trained Batman.. You know what I'm talk'in about. And his resolve is noble. He wants to "Purify the Earth" and what not through destruction. Pretty cool stuff.
(You should search and read "Gotham Uprising Chapter:2- The Assessment" on CBM to see what I mean.)
4.) Magneto
Magneto is a cool villain. Like Ra's Al Ghul in a way he's got his own dangerous possy and a somewhat noble cause. But instead of murderous ninja's, he's got a bunch of deadly mutants he leads, calling themselves the "Brotherhood". He's REALLY powerful, has a smart persuasive way with words, and doesn't kill "his own kind" unless he has to. All that makes for a powerful villain against really, whoever. And magnetism powers?... that's pretty beast.
5.) Graviton
It was hard to choose a fifth villain... There're a lot of villains I like, so Graviton is definitely not the only one I feel deserves to be in fifth place. But anyways Graviton's interesting because he possesses the power to manipulate gravity itself, that's like a RIDICULOUS amount of power. Graviton's number five basically because he's not the type of hero you can just beat, it'll be a messy fight. Just watch "Avengers: Earths Mightiest Heroes Episode 7" and you'll know what I mean.
Whelp, that's my list, there are many other villains and heroes I like (As well as movies) so if you like some of things I have to say then let me know what type of article I should post next.