I think if you look at superheroes solely through the lens of their powers, they're not really relatable. But in their real identities, that's where they often are relatable. Bruce Wayne lost his parents, and is driven by one person's random, senseless act of violence that altered the course of his life. Clark Kent has an almost endless capacity for kindness, and just wants to help others - that's the same charitable spirit that many people can relate to. The best stories with Bruce and Clark have always been grounded in who they are, rather than just their powers.