Let me makes this clear: Superman IV was awful. The villains were bad, the story was worse, and their use of outer space was frankly insane.
But they could have made up for a lot of it with a minor change.
When Superman was fighting Nuclear Man on the Moon, they should have made it the same landing zone that Zod, Ursa and Non attacked in Superman II. They should have shown the crushed lander with the American and Russian flags thrown atop it, the spacesuits with the dead astro and cosmonauts inside, the whole deal. And instead of Superman merely righting the American flag as he did, show him giving those men a moon burial with the flags as the markers for their graves and then pausing for a moment of silent reflection for them.
I think that bit of continuity would have been the stand out moment for the entire film.
But they could have made up for a lot of it with a minor change.
When Superman was fighting Nuclear Man on the Moon, they should have made it the same landing zone that Zod, Ursa and Non attacked in Superman II. They should have shown the crushed lander with the American and Russian flags thrown atop it, the spacesuits with the dead astro and cosmonauts inside, the whole deal. And instead of Superman merely righting the American flag as he did, show him giving those men a moon burial with the flags as the markers for their graves and then pausing for a moment of silent reflection for them.
I think that bit of continuity would have been the stand out moment for the entire film.