I'm of the opinion that every Superman story has already been told, but that that is the advantage of the character. No other superhero has practically entered into modern myth in the same way.
I believe this is why a Superman reboot can't work, and why a "dark Superman" can't work, and why I just don't think a "Superman fights another of his classic bad guys" story wouldn't connect with people.
My Superman would use the fact that Superman has seen and done it all to its advantage. It's an older Superman that has had a thousand adventures. It says "this is how Superman is different from other superheroes, and why he doesn't need an origin retelling, he doesn't need to be reimagined or made more realistic, he doesn't need to be retooled to fit into a cinematic universe".
So the challenge is, "what kind of story do you tell with a Superman who has already done everything?", and my answer is, you just tell the story of Superman.
It's framed as a documentary, showing what Superman is like today in his mid 40's, with a wife and an extended family and friends and all kinds of responsibilities to the world, and also telling his life story in a way that's less about the specific events that occurred and more about how the world viewed him and changed around him for the better during that time. Like, you see him fighting his villains and you see the Legion and you see all the classic covers coming to life, but they're just clips, not scenes.
And all the while that he's recounting his stories and showing you his Fortress, he's humble and charismatic, and he seems to care much more about the people he met along the way and the small moments of helping people rather than the outlandish things occurring around that.>tl;dr
It's a documentary about Superman's life, showing more how the world was better with him in it and how he's a down to earth great guy despite the unbelievable life he's lived.