Darth Vader in his prime could take on anybody. Sidious said that Anakin was more powerful than himself and he beat Yoda and forced him to flee. A Skywalker is the most powerful Sith and Jedi with the lightsaber in star wars history. Vader is so much cooler than anyone in episode 1,2,3 or in the EU series. No contest, Vader Rules
Anakin in his prime vs Sidious in his prime. It'd be close, but i think Anakin would own his *****-ass. Let s even take it a step further...lets say human Vader in his prime just so he could be the ruthless heartless killer that he should be....I'd still say Anakin/Vader over Sidious. THAT would br an epic duel...forget about OB1.