I like Luke and the Emperor, I think the Throne Room is one of the best scenes in the movie!
But Vader (along with Harrison Ford, the ewoks, the Leia is my sister revelation, the lighting and shot composition), sucks. A-dev, I know you've mentioned problems with his redemption and how he's pretty unredeemable and I agree. It's not because of his actions in the prequels though. Just disregarding them, Vader is a piece of crap. No, not because of ANH or Empire, but because of Jedi. He could have defected on Endor if his son, his blood, meant that much to him. But he doesn't. He brings Luke up to the Emperor and is completely fine with his son killing him and taking his place as the Emperor's **** boy. Even goads Luke by suggesting his sister take his place if he doesn't turn.
The whole "I sense good in you" thing is lame. What "good" is there in him? Vader clearly believes in the Force, the Dark Side and the Empire and is convinced that is the right path. Vader doesn't consider himself a bad guy, it's clear in ANH and even Rogue One. He's not enthusiastic about the Death Star, he's not about destroying millions of lives and respects the Force just as much as Yoda or the blind dude in Rogue One. He even considers overthrowing the Emperor. Then by Jedi, all of the that is thrown out of the window and suddenly he's just a slave. "There's no hope for me Luke", "Obi-Wan once thought as you do Luke", "you don't know the power of the dark side Luke, I have to obey my master". He never makes a compelling argument why Luke should turn, he just acts like a victim who has no choice. It's pretty bad. He's "redeemed" because suddenly he decides to make the most obvious choice he should have done earlier? I don't think so. Once you take into account betraying his friends, killing all the Jedi, children, torturing Leia, torturing Han, beating his son to a pulp and lobbing off his hand, etc. he shouldn't get to become a cheesy, grinning Force ghost.
Even in Episode III he isn't that pathetic. Palpatine is a means to an end and he even considers overthrowing him before he fights Obi-Wan.