There have been many different versions of each Star Wars film. It is generally accepted that three versions of the trilogy have achieved "canonical" status: the 1977-1983 "original original trilogy" (O-OT), the 1997 special edition (SE), and the 2004 DVD edition (DVD). For the purposes of this discussion, we shall refer to both the O-OT and SE versions of Return of the Jedi as the original version, and the 2004 version as the DVD version.
First, I will show that Luke and Obi-wan had differing positions on who Darth Vader was. This material has remained the same throughout all three canonical versions of the trilogy.
In A New Hope, we hear Obi-wan say, "Darth Vader, who was a pupil of mine before he turned to evil, betrayed and murdered your father." This summarizes everything Obi-wan believes about the person of Anakin Skywalker/Darth Vader. They are two separate people, and Anakin is dead. This attitude is evident throughout the film; Obi-wan speaks warmly of Anakin, but with disgust to Vader. He addresses Vader by his Sith title, rather than use his personal name or a Jedi title (usually "my young padawan" in the prequel trilogy).
Obi-wan continues to bifurcate the two persons of Anakin/Vader in RotJ, telling Luke, "When [the Emperor seduced Anakin to the Dark Side], the good man who was your father died." Obi-wan has been trained in metaphysics from a very young age; there is no questioning his statement. He firmly believes that Anakin Skywalker is no more.
Luke believes and acts differently. Although initially doubtful of Vader's claim to paternity in The Empire Strikes Back (ESB), he easily addresses Vader as "father" minutes later, when the two experience a moment of telepathic communion. Luke continues to identify Vader as his father throughout RotJ, even as Obi-wan attempts to discourage this line of reasoning:
Obi-wan: You must confront Darth Vader.
Luke: But I can't kill my own father!
Obi-wan: Then the Emperor has already won.
Luke resists Obi-wan's persuasion, and meets with Darth Vader. Although this meeting could be described as a confrontation, it is clear that Luke does not plan to kill Vader. Instead, he reminds him of his pre-Imperial identity:
Luke: I've accepted that you were once Anakin Skywalker, my father.
Vader: That name no longer has any meaning for me.
It is clear that, to both Luke and Vader, the name has changed, but the essential person has remained. Neither one considers Anakin Skywalker dead the way Obi-wan Kenobi does.
Luke continues to identify Vader with Anakin throughout their confrontation in the Emperor's throne room. Ultimately, as Luke writhes in pain under the Emperor's Dark Side assault and calls out, "Father, please!" Vader decides to act as a Jedi would, and dispatches the Emperor at the cost of his own life. There is no evidence that a discorporate Jedi spirit is reinhabiting Vader's body, or that the decision to save Luke from the Emperor came from anywhere other than Darth Vader. Wounded by the Emperor, his life support systems destroyed by lightning, Anakin Skywalker throws away the trappings of his life as Darth Vader to look at Luke one last time for the first time, tells Luke, "You were right about me. Tell your sister, you were right." Having made his final statement, he dies. Luke burns his father's body, still caparisoned as Darth Vader, in a private ceremony on Endor.
The next scene is where the original version and the DVD version differ, and where either Luke or Obi-wan is proved right. After Luke has cremated his father's body, he returns to the Ewok village where the Alliance commandos recruited their indigenous fighters. A number of Alliance officers are celebrating their victory against the Death Star, but Luke is in no mood to celebrate. He moves off from the throng, and sees three Force spirits. Two of them he immediately recognizes as Obi-wan Kenobi and Yoda. The third, he realizes, is his father.]
In the original version, his father is an old man, perhaps old beyond his years. His face is lined, but he smiles at his Luke. He is the archetypal father of an adult, who has suffered much in his many years, but looks with hope and pride upon his offspring. Luke was right about his father. Anakin Skywalker didn't die when he became Darth Vader; he grew old, and died old. His Force spirit reflects this.
In the DVD version, his father is a young man of perhaps twenty-five or thirty. He appears approximately as Anakin did in Revenge of the Sith (RotS). This supports Obi-wan's position, that Anakin died when he became Darth Vader. (The exact time of death is unknown, but may be determinable after careful study of Anakin's spirit and his appearance throughout RotS.) Curiously, this means both that Luke was wrong, and Anakin/Vader was wrong in proclaiming that Luke was right.
One wonders what occurred between 1983 and 2004 that compelled George Lucas to revisit the central conflict of RotJ and choose a different winner. Is it merely the result of aging? Does Lucas look differently upon his own father, now, or his role as a father? Was the internal logic of the Force reconsidered throughout the writing of the prequel trilogy? Further research is warranted, but it would require more biographical information on Lucas and in-depth information on his writing process than I have available.
Scruffy's gonna die the way he lived.