OK, I have a lot to say here, so bear with me…Why do so many people think Vader is so powerful? He is NOT!!! I have said this a million times and I honestly don’t want to repeat it again, but since this common and understandable fact just can’t seem to go through some people’s heads, I have no choice but to repeat it again: Vader in the suit is MUCH weaker than Anakin in ROTS! This is confirmed by Lucas. It makes sense too since he lost more than half his body and the suit greatly increased his weight and reduced his agility.
The reason why Darth Vader is so feared by the time the OT comes is because he is the only visible Force User. All the Jedi are wiped out, and Obi-Wan and Yoda (the only two Jedi who survived the Jedi genocide) were both hiding and completely cut themselves off from the rest of the galaxy. The Emperor is also at his throne room doing absolutely nothing. Other than that, no one else can compare with Vader, because all Vader has to do is choke them or something.
When Vader encountered with Obi-Wan in ANH, like Vader himself, Obi-Wan was also considerably weaker than he was in the prequels because he hadn’t really practiced his powers for some twenty years. When they fought, Vader didn’t really seem to gain an upper hand and Vader didn’t defeat Obi-Wan, Obi-Wan gave in. It automatically took the air out of that knockout blow. When Vader fought Luke in ESB, Luke only had a few days of training and I admit that at first, Vader was toying with Luke, but after underestimating Luke for a while, Luke lands a blow on Vader’s shoulder. Vader therefore got serious and cut Luke’s hand off, that IMO was the only battle he actually won, which really isn’t that impressive. But when he faces of against Luke in ROTJ, he got OWNED!! Big Time! And please don’t say “Oh, Vader was holding back and let Luke beat him”! That is a pure conjecture. Why did The Emperor want Luke SO badly? Because he knew Luke could take down Vader. Vader was much past his prime time because of the suit, while Luke was only a young force user capable of great potentials. Think about how screwed the Rebels would be if Luke could be converted. Why did Yoda say “No more training, do you require” when it was obvious that Luke was no where NEAR completing his training? Because Yoda, too, knew that Luke, despite his lack of training, was capable of defeating Vader. And while they were fighting, I think it was Luke that was holding back. Luke kept stopping the fight and Vader kept starting it again. When Vader mentioned Leia, that was when Luke really tried. And when he did, He completely owned his daddy, you could tell because when Luke was jabbing at Vader with all his might, Vader was completely confused, he had no idea what to do. He missed parry after parry, and ended up getting his hand chopped off. He was lucky that Luke still had poor aim, otherwise he would have been wasted earlier than that. Plus, after the battle, Vader was breathing like he ran a marathon, while Luke seemed to be breathing perfectly fine.
So honestly, you Vader fans are saying he is powerful because he is cooler, or has a better reputation, not because of his actual power and skill. Darth Janus is 100% correct. Reputation and importance to the series has absolutely nothing to do with how powerful someone is.