I had read some time ago about the unique attributes of the Trinity(Superman, Batman and Wonder Woman).
Superman(1938-present)- Despite his super powers and abilities, he is an orphan of tragedy. He lost his birth parents to an event noone could ever imagine; the destruction of Krypton. It is from Jonathan and Martha Kent he learns about everyday functioning on earth. He is learning about himself and his abilities. These values he carried with him thoughout his life made him what he is today. In 1988, I learned an important lesson from Superman; you don't have to have super powers to be a good person. All one can start with is a good heart.
Batman-(1939-present)- Like Superman, Batman grew up a child of tragedy. He witnessed the murder of his parents. He then studied and trained to become a crimefighter. He turned his pain into a triumph. And he rose above it. Bruce Wayne's transformation is very relatable. We all have been through some kind of tragedy in one form or another. But, unlike Superman, the fact that there is wrongdoing everywhere one turns is also a reality. He has a very keen and analytical mind. He is an excellent and highly adaptible hand -to- hand combatant. Everyone can relate to Batman because, though he has no super powers like Superman, he puts his all into everything(his mind and body).
Wonder Woman(1940-present) - It can be easily said that Wonder Woman was girl power before the phrase was created. She was of the mindset that the world of men was not compassionate, hateful, fearful, violent and destructive. And she wasn't wrong. She is the epitome of everything she stands for. She is beautiful, compassionate, strong and courageous. She is the creation of William Moulton Marston, a psychologist.
We can find a lot of things to relate to with these and other heroes.