I could have sworn that they specifically said that Superman was dead. As in dead-dead. I remember a conversation between the Eradicator and the returned Supes (in Superman
82, I believe). The Eradicator said how he was able to come into being and Supes questioned if he really died, to which the Eradicator said "No, Ka-El. You were dead." I don't have the trade in front of me, so I cannot check. But I am pretty sure he was dead and the Eradicator jumpstarted him when he syphoned off Supes body.
If that has since been retconned, I cannot speak to that.