Falling down a hole is not the same as being blasted by the super death ray gruesome murderizer 5000 and palpatine wasn't a puddle of blood on the floor. Jedi literally have a technique called Slow Descent where they use the force to prevent injury from falling at great heights. Palpatine was the second most powerful force user next to Anakin at the time he was alive. He was more than powerful enough to levitate himself and he was still alive when he fell down into the hole.

Also darth vader could have dragged himself to an escape pod. The guy had a cybernetic life support system. It could have restarted his heart seconds after Luke left him on the floor.

All in all the original trilogy gave deliberately gray area endings to two of the most iconic villains in cinema.