Originally Posted by
Rise
Superman's problem isn't being boring, his problem is being outdated. His philosophy about Truth, Justice and the American way is a joke in today's era considering how "the American way" casued so much harm to many people in the world (my region which I live in suffered from the so called American way and its justice).
Luffy is a product of his time too. His type wouldn't be accepted or well liked with today's generation which is why you don't see much of his type anymore. The only thing Luffy has over Superman is being written by his original writer in consistent series with already established fanbase while the latter has a divided fandom due to the many different takes that existed of him through his history. It's why I say it's unfair to compare the two.