Kenobi wasn't resurrected. He became a ghost. That's dead.
Maybe my materialist/antisupernaturalist bias is showing, but for storytelling purposes there's no practical difference between a ghost and a resurrection. In both cases, the finality of death is undone and the dead are free to interact with the living, make and carry out plans, influence the universe, etc. It's not like Kenobi was a shade combined to the underworld, or doomed for a certain term to walk the night. He just tricked Vader into discorporating him so he could act in secret, unencumbered by a physical shell. He wasn't a classical ghost segregated from the living world, a Shakespearean soul in torment, a Victorian table-knocker, or a modern residual haunting. He was just a non-corporeal living being.
And he wasn't the only one. By the end of the Trilogy, we had also seen Anakin and Yoda in this state. That is, every Force-sensitve bar one who physically died wasn't really dead. They were shown dying, on film, then the filmmaker resurrected them. As "ghosts." This is hardly surprising--the same filmmaker filled his universe with telekinesis, telepathy, and clairvoyance, so ghosts fit right in.
Now, does Palpatine's "resurrection" fit in as well? I'd argue that it does. Remember, when DE was written every other Force-user was able to maintain their consciousness and personality after death. Why not Palpatine? The circumstantial evidence suggests he could. And--in a universe full of telekinesis, telepathy, clairvoyance, and ghosts--who's to say possession doesn't also occur? It's a logical outgrowth of Yoda's philosophy and the evidence for the soul existing independently from the body. The body is crude matter, the person is the soul, and the Force binds everything together. So the body is just a meat puppet animated by the soul. A sufficiently powerful soul could animate another body. And so Palpatine did.
I thought the Dark Empire portrayal of Palpatine was pathetic. In ROTJ he was a distinctive villain, whereas in the Dark Empire, Dark Empire 2 and Empire's End comics has was just a non-disticntive cliche villain and rather annoying. And they didn't bother to draw him looking anything like Palpatine.
You will note that I was including the DE Sourcebook in my earlier comments on DE. Most of what we know of Palpatine's plans for his theocracy come from the Sourcebook. (And probably later books that I have not read.)
Anyhow, the bathrobe tyrant of RotJ served as a decent nemesis for Luke Skywalker after Lucas decided to make Vader more sympathetic. But nothing about him screamed "galactic emperor" or "dark overlord." He seemed to have no plan or vision for the empire he had created. If it was just an oversized bodyguard to support his lavish lifestyle on Coruscant, that's great, but hardly distinctive. Dark Empire and its ancillary materials defined those distinctive elements that made the Galactic Empire more than just a slightly overzealous version of the British Empire in space.
Re: Boba Fett, I am always surprised by how many OOT fans ignore the bit about the "pain and agony as you are slowly digested for a thousand years[*]." Taken at face value, Boba Fett could not possibly have died during Return of the Jedi. If we assume that Jabba was exaggerating by several orders of magnitude ... Boba Fett could not possibly have died during Return of the Jedi. I'd like to think anyone who fell into the Pit of Carkoon died quickly and painlessly, because I have an aversion to torture, but Jabba does not, so I think they survived in the Sarlacc a long time. And I think the guy covered in armor, weapons, and a jet pack could maybe get out. Turns out the people who Lucas's corporation hired to continue Star Wars agree with me on this one.
[*] You could try to knock a few centuries off the survival time by arguing that most of the digestion must be post mortem. However, Threepio's language is clear: The pain and agony are coterminous with the thousand years of digestion. How a human being could survive being lunch for a millennium is something else that the DESB explores. And it gives us this line which elevates an otherwise average roleplaying supplement to great literature: "Half a kiloton was excessive, even for Fett."