He was a whiny teen. Luke Skywalker just accepts his fate. In an ACTION movie, that is important. Leave the shallow soul searching for MTV. The problem with the movie is that Darth Vader it truly and wholy evil. The "saving" at the end of Return of the Jedi was already bad enough (in the books and expanded universe it is made clear that he can't cross over nearly as easy, hence the reason to burn the corpse where Yoda and Obi-wan just faded away) but it still doesn't sit well with the hero ending of the bad guy being blown away, but is excused because it is different enough to be seen as original.
But he AIN'T a hero character. And in the first three movies you are supposed to care about this guy who really is not going to end up saving the day. It would be like making a movie about Adolf Hitler's youth and expecting people to root for him. Sorry, no. And there was a remote possibility that we could have cared, if we had seen him fighting the dark side only to be tricked fatally in the end in a way nobody could forsee. But the entire 3 movies are like a Punch and Judy show, with the audience screaming "look out behind you" and punch looking the wrong way and saying "where". Hilarious when 4 year olds see it done in a good puppet show, but the political antics were beyond young kids and below adults. Where were those supersmart jedi, were was the mastermind of the emperor. No action hero to save the day, no intense manipulation by unseen puppeteer masters who turn wheels within wheels. Just... well just the 3 prequels which told a story that could have been told in a simple expanded universe book in a way that would not have focussed on the villain but on a new hero whose path crosses that of the villain.
There is a reason this guy takes 70 minutes to tear the movie down, because the prequels are really that fucking bad. Not the kinda bad that you get when a producer gets his hand on something he doesn't understand (Uwe Boll) or the producer just can't direct (Plan 9 from outer space) but the kinda bad that arrives when a lot of very talented people forget just what the fuck they are good at doing.
The simplest example of this is the CGI battle on the grassy plane. What did CGI do well in those days? Tech scenes, hard corners, steel and concrete. So what did they render, lush grass land. It looks fake! They managed to get a green lawn which you can shoot for real on any golfcourse looks horribly fake.
And if you think 20 minutes is 1/3 of the movie, then your brain must have carefully restructured itself to shut out the most damaging memories, memories that if they were to surface would turn you into a bliddering murderous psycho.
Proof, you think the movie could be fixed. Amazing healing capacities the brain has. I can remember it all, but I am sane! Ain't I Mr. Fibble?