1990osu said:

It makes you wonder if they are considering reshooting ROTJ's ending for the sequels, or perhaps beginning Episode 7 with a replay of the throne room scene going differently...

That's not true. That's IMPOSSIBLE!

I agree that the scene strains credulity however. The first time that I watched it, I was absolutely sure that Luke wouldn't be turned to the Dark Side. There was no question in my mind. Luke was a hero. He was us, the audience. And so the scene played out. The point of the scene, I think, was to show the audience that he who can make you angry can control you. The only question that Luke had was in what Vader was thinking when he let Luke escape Cloud City. When that scene is reenacted with Luke as the antagonist, he feels the same as Vader in that moment. In that moment, father and son are as one, both equally culpable in their use of the Dark Side. However, Luke is still himself. He used the Dark Side, and was not turned. So here was the answer to his question, about whether Anakin was in some way still alive. Indeed he was.

"Never. I'll never turn to the Dark Side. You've failed, your highness. I am a Jedi, like my father before me."

He states that Anakin yet lives. Therefore he is saying that not only did the Emperor fail to convert him, he failed to even convert Anakin.

Of course, I disregard the prequels in this analysis.