Spider-man, for me, has always been the most relatable of the major superheroes.
It's not just that he wears a full-body-concealing costume, so that anybody (or, at least, anybody skinny and male and able-bodied) can easily imagine themselves in his place. It's not just that his power-level is reasonable - not just a guy in a mask, but not a god among mortals either. It's not just that his powerset allows him to scope danger, swoop in, and immobilize people in a way that make superheroing vaguely ethically defensible. It's not just that he's the hero, so he always wins.
And no, it's not just that I saw him on TV a lot while I was growing up.
Spider-man is relatable because, at least in his own mind, he has good reasons for doing what he does. Like the death of Batman's parents, Uncle Ben's death is told and retold every time Spidey's tale is re-adapted because it helps make sense of who the character is. It illuminates Peter's feelings of responsibility towards his loved ones and towards the entire world.
And you know what? He doesn't always win. Spider-man gets hurt and beat up and he makes mistakes and he loses and the papers call him a monster. And he gets disillusioned and he gets heartbroken and he quits for a while, but he always inevitably comes back.
The one thing about Spider-man that I can't relate to, though, the one thing that isn't justifiable is the way he shuts his loved ones out of his double life. Sure, he doesn't want Aunt May to worry about him or to be afraid, but cutting her out completely, I think, shows a profound lack of respect for her - he assumes she won't be able to handle it. It isn't until he opens up to Mary Jane that he is able to have a real relationship with her, which, in turn, helps him become a fuller, more adult, more real human being.
We shall ignore the events of the One More Day storyline.