I'm not saying he's the greatest by that point. I admit he still lacks a lot of control and dedication. btw, the fact that they couldn't fight fast has a lot to do with how we view them now. Had they had the materials they had now, whose to say both Vader and Luke wouldn't have been twirling and whirling like duels in the PT
Luke becomes the greatest Jedi ever, and the most powerful force user the galaxy has ever seen. Look at who his father was and how quickly he responded to the force. He will surpass everyone, it just takes him a good 20-30 years after ROTJ