I have to say when he's done well, yes, he is the greatest comic book villain of all time, he has so many great quotes.
"Oh yes, I forgot a very left-brained personality. Let me put this in itty bitty words for you. You want Jennifer, you do as Dr. Doom says. Or as you would put it so charmingly: Hulk no smash!"
Gotta say Simon Templemen (Kain himself) was a great voice for Doom.