^If he would've revived eventually on his own when exposed to sunlight, then he didn't die, regardless of later retcons. If you can recover from it through your own natural healing processes, then by definition it isn't death. Except maybe in the most technical, clinical sense, as in a case where a human's heart stops for, like, 20 seconds and then restarts on its own.
For all intents, Superman was dead. Very dead. It was made explicitly clear in the Death/Funeral/Return storyarc that he was dead. Later DC even used the fact that he was dead as a partial explanation on how other heroes were able to come back from the dead (it was something like his returning opened the door from the other side or some such).
I don't know if this was retconed, but as far as I am concerned and the original tale gave us, Superman was dead.