I want to make a comparison here between some of the most powerful beings in Middle-Earth during the Third Age. 

I know Sauron was the most powerful of all even when he lost the ring, but one of the rare comparisons one can find is Galadriel vs Saurman in the Hobbit, where Galadriel seemed to be superior and silenced him to hear what Gandalf has to say.

Also Galadriel vs Gandalf the White, and Gandalf the White vs the Witch King of Angmar: in the movies Gandalf seemed almost powerless against the Witch King, which I don't think to be accurate?

Is there some kind of 'rank' of power amongst these powerful entities?