In TROS the Emperor is alive. Ok. Sure. I accept that with a grain of salt, but its not specified how he survived.
He survived being electrically shocked, throw down a 300m+ shaft and some kind of force/electrical explosion, then very soon after (15min?) the explosion of the entire moon he was in. Those are really long, nigh on impossible odds of survival. As a GM I wouldn't even let a player roll for odds that long. They have a better chance of finding shelter on a planet with no breathable atmosphere naked.
So here is my point. This undoes every death where we loose track of the body in the entire trilogy of trilogies. Han Solo? Sure he survived. Why not? He only got stabbed (the wound was cauterized), and fell a few hundred meters, there was no force/electrical explosion, and the moon he was in exploded. Seem like the exact same scenario as the Emperor with one less explosion. Why couldn't he survive?
Having the Emperor live basically undoes every death that we don't explicitly keep track of the body. If we don't see the head come off or a force ghost, they can be alive.
Please don't forget Darth Maul further proves this. (Solo and The Clone Wars Animated Series)