I keep hearing things from Prequel bashers like, "The Vader of the original trilogy was a man who emanated the feel of decades of slow slips down a slope of self justification and small concessions, until it was too late to look back. ". And it makes me wonder what movies they watched.
Number 1, Obi-Wan said he was "Seduced" by the Dark Side. You don't use that term to describe a slow descent, you use it to describe someone being offered something and accepting it.
In ROTJ, the tension of the final confrontation is predicated on the idea that Luke could enter that room good and come out evil, simply by what happens in that room. I would be more sympathetic to Prequel haters if their complaints came from the opposite direction, if they claimed that Anakin's fall had too many factors to it utterly undermining the ablity to claim Luke faced and resisted the exact same temptation.
But Luke was demonstrated as having the same basic weakness, he really couldn't handle the thought of losing those he cared about either, as his leaving Dagobah in Empire demonstrates. Leia possibly didn't as much, when she lied about where the base was while Alderan was threat, she had to know that cold have only stalled the threat, regardless of her not for seeing Tarkin blowing it up anyway.
Yoda's iconic "Fear leads to Anger" speech from Episode I lays out Anakin's path. And in a sense he already went through all those steps in Episode II, it was just a matter of making the formal decision to become a Sith. But when he killed Dooku it can be argued Sidous already achieved what he was trying to get from Luke in ROTJ.
I'm kind of tired of ends justifies the means always being the default reason for a Hero's fall. And while you can kind of say Anakin's fall was Ends Justifies the means, it was an inherently selfish end, he was willing to kill many to save one or two persons.
Vader in the OT never came off at all like a villain who saw himself as a hero. He and the Emperor both talked like card carrying villains. You don't willingly call your side the Dark Side and talk about being fulled by Hatred when you think your'e the righteous ones.
It was always apparent that becoming a Sith Lord meant a concise decision to choose Selfishness over Selflessness. I can somewhat understand not getting that from the OT alone though I see it there just fine. But I really don't get the EU fanboys who couldn't figure this out from the EU available before Episode II came out, like KOTOR.
Even going off what we thought the story was in Episode IV, Anakin's "death" was around when Luke was born, so it'd been 20 years since Vader became fully Evil and Anakin was "dead".
If Vader had fallen because of just a slow descent of power corrupting him as he used the ends to justify the means. I really would not consider his being saved by a desire to save his son plausible. I know it might seem really offensive to some people to dismiss the inherent love a father is supposed to have for his son even when he never raised him or knew he existed till 6 years prior. But if family wasn't why he turned I don't see it logical to be why he turned back.
What watching ROTJ with the Prequels in mind tells me is that what was important was that Luke, (and Leia), were what was left of Padme. Saving him kind of meant saving Padme, Vader's fall isn't complete in ROTS till the NOOOOOO scene, because remember he would have assumed the child was dead too, that'd lost everything he sacrificed his Jedi oath for.
Another thing I like about viewing the OT after the Prequels is how it's not as simple as Luke is the heir of Anakin and Leia of Padme, though that works in regards to their basic narrative roles, in terms of personality both are a combination of both. I've talked before about how I see Anakin in Leia, it's really Leia who inherited Anakin's arrogance and brashness. I can't really verbalize what I see of Padme in Luke, maybe it's that in a certain sense he is more of an idealist then Leia.
Point is, seeing Luke being electrocuted brought him back to two things, one when Mace Windu was being electrocuted and he first made the decision to become a Sith. But he also saw Padme in Luke.