I don’t believe that all dead people come back to life as ghosts because only a small amount of ghosts are actually ever felt. With so many people dying, people only have felt the presence of a few ghosts. Therefore, it is hard to believe that all people die and become ghosts. Instead, it seems that some people die and they don’t go straight to heaven or hell. They are somewhat stuck in limbo. During this time, they are waiting for their judgement day.
Although, there is a possibility that everyone who dies becomes a ghost, but only a certain amount of ghosts for whatever reason actually are felt or sensed. The others remain away and are not noticed by humans on Earth.