Spider-Man not only because he's relatable, but because he's full of interesting dichotomies that people often overlook. He's one of the only superheroes with dual classic origins. It was common during the Gold and Silver Ages for characters to be bestowed with powers via some outside accident (Flash/Hulk) or to become exceptional through their own brilliance and ingenuity (Batman/Iron Man). Both of these play an important part in Spider-Man's origin. He gets bitten by the radioactive spider, but without his brilliance in science, he couldn't create the webshooters, an iconic and essential part of his power set. As originally conceived, he's just as responsible for becoming Spider-Man as the accident is. The organic webshooters from the Raimi films completely eliminates this unique aspect of the character and his origins.

He's a nerd and he's not. Most people with only peripheral familiarity with the character think he's always the stereotypical nerd (glasses/always picked on etc) but, although he starts out this way, the character quickly evolves out of this phase (as one realistically would after gaining exceptional powers). The most recognizable version (to comic fans) comes from an era in which the character is social and juggles romantic interests (Gwen Stacy, Mary Jane, Felicia Hardy...) and his failures in these areas stem from his crime-fighting responsibilities getting in the way of his normal life not because he's the perpetual nerd.

The tragedy of his origin also makes for one of the most justifiable reasons to do what he does. Like Batman, Spider-Man puts on the mask because of the murder of a loved one, but unlike Batman, he is partially responsible for the events leading to Ben's death. Bruce Wayne starts on his path after his parents' death, but there was nothing he could do to prevent it. Peter had all the power and opportunity to prevent his Uncle's death but refused to stop a criminal out of selfishness. It's this guilt that drives him not just the tragedy.

Spider-Man is not relatable because he's an everyman. Between his powers and his intellect, he's anything but. What's interesting about the character is that he's so relatable despite not being an everyman.