Well, I like Sith in general for the same reason I like (or to phrase this in a much better way, respect) some psychopaths. They have this natural ability to block out traits like remorse in order to further their goals without hindrance, they are masters of manipulation, highly intelligent and have an amazing ability to read people (what makes them tick, their underlying emotions and intentions) - and perhaps most of all, they are ridiculously driven. Not much will stand in their way if they want to get something done. You can't scare them, can't make them submit to pain, and you can't convince them that they're wrong, they just get shit done no matter what.
It's the type of personality that could make some great things happen in the world if it was applied positively, because of the sheer motivation backing the individual, but a lot of times psychopaths/Sith tend to be self-obsessed serial killers or high-ranking businessmen/politicians/people in power who abuse that position of power.
I'd probably pick Plagueis for a Sith I like. Maul is also one of my favourites because despite the life-long career of evil he was forced into from infancy, he's still managed to show some levels of humanity - on top of that, he's still a ridiculously driven, highly intelligent, tactical, manipulating, murderous psycho who gets shit done.