As I discussed in the article, the turn-back-time ending was originally scripted for Superman II (not sure how the first Superman was to end originally). Instead, they used the turn-back-time thing for the first film, to resurrect Lois during the earthquake. It is a better climax to the first Superman (it still doesn't make a lick of sense, but it's more emotionally resonant and feels more forgivable as a leap of logic in that film). What Donner planned for the ending of Superman II is unknown, as they would obviously have had to change the plan (as Lester ultimately did, to rather better effect in my opinion). :)