That's something i don't have a hard time agreeing with. In India there was a superhero show in the 90s. Shaktimaan.
http://https://en.m.wikipedia.org/wiki/ShaktimaanThat show was a massive hit. Kids were mad for Shaktimaan. The character shares a lot of similarities with Superman even though his powers were based on magic/Indian mysticism.
You have a superhero who would be considered OP by many. He used to work as a newspaper reporter. While not exactly mild mannered, the writers were definitely copying Clark Kent. There was a version of Lois Lane as well. They had a mad scientist like Lex Luthor. Though he wasn't Shaktimaan's archenemy. They even got a version of Kryptonite. Shaktimaan's personality was quite similar to Superman. Many would call him a boyscout. In fact, they got segments at the end of the show much like PSAs for kids.
So, this was a big success as late as 90s and early 2000s. It was targeted mainly towards kids. But it wasn't a 'kiddie' show like say Teen Titans Go! and adults could watch as well. So, in a way i was a fan of Superman before i even knew who Superman was.
Its to be noted that this 'Superman' didn't have to face a Batman or a Spider-man or an X-Men to compete for attention. It was at the time of its run something unique for Indian viewers. I think the biggest competition it got was a magic ring wearing superhero kid. While fairly successful, that show couldn't compete against Shaktimaan at all. You would think a kid superhero would have better appeal for kids. But nope.
Its one show which didn't end due to falling ratings. Rather due to contract disputes. Maybe Superman as a character has more appeal for kids then adults.
And that's where they should target. If they make movies keep kids as the main target, but be enjoyable to adults as well.