I don't find Palpatine boring, but he's only as interesting as he's a competent villian. All he wants is power and revenge, which makes him a bit on the dull side. At least Vader was loopy enough to want love and crazy enough to try to force it; also, Anakin craved order in a way that lead only to destruction.

Dooku, I really do think, ruined himself trying to follow Jedi ideals -- justice without compassion is a sword that cuts back on the wielder in the end. And his telling the exact truth was a brilliant tactic, though poor Obi-Wan completely failed to see it.