What if Vader wasn't Luke's father in the original trilogy?

What if the big twist never occurred (you can imagine a different ending for the saga, doesn't really matter here)? What if, when the prequels rolled around, people expected Anakin and Vader to be separate characters, but Lucas still treated them as one? How would the movies be received as people gradually discover the dark truth as the story progresses? How would it alter people's perspective on the originals?

Thread inspired by The Ellimist.

I expect people wouldn't take it well. Without any sort of buildup or reveal in the originals, it would feel pretty empty.

ESB would not have been nearly as appreciated by the fans as it was when it came out. The plot twist is one of the most important elements of the movie, that adds a lot of depth to Anakin’s story. Discovering it in the prequels would have been a “meh” choice from Lucas as i think the fans would have considered it a forced choice. The “I am your father scene” is still an iconic moment of SW, and I cannot think about the saga without it.