Funnily enough, I had pictured the Vader conversion scene almost exactly like in the movie - in a dark, reddish room in front of a giant window... Anakin gets the same offer as Luke and accepts.

Though my memory could be playing a trick on me, so I'm not sure.

Obviously, it was supposed to be dramatic and serious, and Vader's decision conscious, not as falling for a con. Without all the narm and ham and all...

other than that, dunno. More authentic personal drama like in V and VI, more "hero in dragon's lair" situations full of doubt and despair... something like that.
Just as RLM pointed out, the prequels took the imagery, but forgot the dramatic context.