I only just finished Kravens Last Hunt yesterday so he would be probably number 1 or 2, with the Green Goblin in the other spot. I also like Carnage for the random insanity factor. He was a psychotic serial killer before he got any powers and he hasnt really expanded his goals since. Maximum Carnage wasnt well written but it reminds me a lot of The Dark Knight with Carnage in Jokers role. He had no interest in power or fame and he didnt want to rob banks or steal super weapons, he just wanted to show people that they should stop living with rules and regulations. Like the Joker he did this with random murder and violence. Mind Bomb is a really weird comic that shows just how crazy the dude is. I loved the Flowers for Rhino story but I wouldnt say Im a big fan of his in general.
I like The Lizard, The Green Goblin, Doctor Octopus, Venom, The Vulture, The Sand-Man, The Walrus (in a "So bad he's awesome" kind of way) and Electro. I don't like Hydro-Man, The Jackal, Mister Negative, Carnage or The Hobgoblin. I also don't like how there are almost no female Spider-Man villains at all, I don't suppose The Black Cat really counts as a villain any more, and there haven't been many others.
Electro's body is constantly giving off electricity, Shocker just has gloves that give off shock waves.