Well, he is a boring villain and I am not sure if there is much to say about him, but he fits the story and narrative of the LotR, and I take such a villain over one that is badly writen with debth for the sake of debth. I mean LotR is as black and white as you can get, which is 'ok' for this kind of fantasy. Don't forget, LotR was pretty exceptional some 60 years ago. But for me the real villain isn't even Sauron, but the one Ring, just as how the humans and elves are not the real heroes, but the hobbits. Not really super deep, I know, but you have to give Tolking at least that much, that he isn't just doing shiny knight against super bad dragons here.