For some reason people misunderstand this character. He did not begin as a righteous senator, he was merely acting the part so that he could create an image that he could use to his benefit to gain real power. This misinterpretation of his intentions goes to show just what a great manipulator of people he is.
In reality, he is easily one of, if not THE greatest villain ever created. This sith lord knows what true power is. Along with being able to wield a lightsaber and using the awesome force storm ability(shooting lightning from his hands), he gained power through the use of politics and manipulation. He did not only improve his abilities, he also chose to gain powerful allies to use as he pleased. With this idea in mind he gained the support of the Galactic Senate and gained the (fairly) loyal service of another of the greatest villains(Darth Vader). Through these actions he created a barrier around him that was nearly impenetrable and he was able to single handedly rule the galaxy, wipe out nearly all of the jedi, and basically just impose his will upon the entire galaxy.
Normal villains such as Venom(Spider-man), the Terminator(The Terminator), Magneto(X-men), the Joker(Batman) and even Darth Vader are all a terror to those who fight for truth and justice, but none of them could outlaw truth and justice nor could they deceive the universe into thinking that they are fighting for truth and justice.
Contrary to popular belief Darth Vader is really a fairly pitiful villain. When he was young he went by his true name, Annikan Skywalker, and was basically just a pain-in-the-ass crybaby who never really did much besides win a pod race and beat a weak apprentice (Darth Tyranus). He was later defeated by Obi Wan and became a pitiful excuse for a human being. After being rebuilt into a badass looking cyborg who pwned some underlings with the choke(the one truly great thing he did) he was beaten by his son. Basically, he seems like an amazing villain, but if you look close he is nothing much, he just has a great image.
cool things:outfit, breathing, force choke, sounds awesome, wipes out some sand people in rage, force choke(it simply has to be said again, it is truly amazing)
crappy things:beaten by Luke(who was whiney and un-cool), beaten terribly and utterly by Tyranus in Episode II, was second in command to a non-force user on the ship he was on in Episode IV, whines ALL the time and cries as teen Annikan, loses to Obi Wan(and loses most of his limbs), never even becomes a master