Some years ago, somebody set out to discover who the most recognizable figure in the world was. They expected it would be Jesus Christ. They were wrong.
The individual recognized by the most people on the planet, including barely-contacted tribes: Superman.
Humans have a deep psychological need for gods and heroes. In a world where the three big monotheisms hold much power, fictional figures come to fill that need. The superhero is an archetype not so very different from David or Gilgamesh, and the modern superhero is even more recognizable. Most people know Superman’s logo or Batman’s on sight, or would instantly recognize Captain America’s shield. At a deep level, we know who these people are. They started out as simple fictional characters; indeed, their popularity was influenced by the Comic Code Authority, which made it hard to write the horror comics that were actually more common at the time. They became something else. Myths, filling a psychological hole. Indeed, Marvel’s Thor directly crosses over between the two, turning a pagan god into a superhero.
Why do we need superheroes? For the same reason our ancestors needed gods. To solve the problems we cannot imagine being able to solve ourselves.