I choose to believe that he's the main antagonist of the original Star Wars. I like him the most because he's not trying too hard.
Vader's a bit over-it with his imposing nature and dark voice, but I think his, along with the Emperor's, writing makes up for it.
Still, I would have preferred someone like Chris Greenam for Vader, and Clive Revill for Palpatine (I'm big into British talent).