How powerful is Vader?
It's an interesting question for me, with a fair number of power scaling ramifications for the EU.
Today I was remembering a quote by the lost tribe saying roughly, "Vader is one of the most powerful Sith of all time." That's pretty impressive when you consider they knew about Hord, Sadow, and the rest of the ancient Sith, not to mention all of the Sith in the lost tribe's history.
Also, it seems pretty clear to me that FOTJ Luke > Vader as well as RoTJ Sidious > Vader.
So thoughts? Specifically who do you think is essentially equal to Vader for
1. Force powers
2. Lightsaber prowess
P.S. This is for RoTJ Vader.