If I were to film the next Superman movie--assuming that a continuation of the Donnerverse is no longer on the table--I would make a period piece set in the 30's or 40's. I would give it a stylistic look reminiscent of the Fleischer cartoons.
The movie would portray Clark Kent as the disguise, not Superman.
Although no other superheroes would be shown, there would be indications that other DC heroes do exist. A character might mention that she has relatives in Gotham City, or Lois Lane might be excited that she got to interview the millionaire Bruce Wayne last week. Other heroes would take no part in the plot, although they might have cameos in sequels.
Lex Luthor would also take no part in the plot, but there might be a brief reference to the fact that he exists and that Superman has occasional run-ins with him. Perhaps something like this:
Olsen: Gee, Clark, do you think Lex might be behind all this?
Kent: I doubt it, Jimmy. Superman says that this scheme just doesn't look like Luthor's handiwork.
The movie would portray Clark Kent as the disguise, not Superman.
Although no other superheroes would be shown, there would be indications that other DC heroes do exist. A character might mention that she has relatives in Gotham City, or Lois Lane might be excited that she got to interview the millionaire Bruce Wayne last week. Other heroes would take no part in the plot, although they might have cameos in sequels.
Lex Luthor would also take no part in the plot, but there might be a brief reference to the fact that he exists and that Superman has occasional run-ins with him. Perhaps something like this:
Olsen: Gee, Clark, do you think Lex might be behind all this?
Kent: I doubt it, Jimmy. Superman says that this scheme just doesn't look like Luthor's handiwork.