We've all dreamt of gaining superpowers and saving the world. The Marvel stories allow us to see that fantasy in action. Marvel's roster of heroes consists of many people who lived normal lives, just like the rest of us - ordinary people suddenly thrust into extraordinary circumstances. But their reactions, the way they respond to these circumstances, is deeply human, and thus deeply relatable. Peter Parker was an ordinary high school kid who faced many typical high school problems - grades, bullies, a crush, etc. But on one fateful field trip, he was accidentally bitten by a radioactive spider. This incident granted him special abilities, like enhanced strength, reflexes, and the ability to climb walls. After his uncle was killed in a robbery, Peter decided to use his powers to fight crime and defend the weak. He became Spider-Man, the web-slinging crime-fighting vigilante we all know and love today. Spider-Man has fought many villains, from simple crooks to multiverse-ending entities. His life - in many different retellings - has gone through incredible highs and devastating lows. However, he's still a kid at heart, and it shows in the way he interacts with the world around him. In all things, he tries to stay true to his morals, to cherish his loved ones, and to never forget that "with great power comes great responsibility." Stories like that of Peter Parker - as well as many other Marvel heroes, like Captain America and Daredevil - are so compelling because they show how ordinary people - like us - are capable of doing the right thing and achieving greatness. They inspire us to follow in our heroes' examples and strive to test the limits of our capabilities. DC's godlike heroes could never hope to achieve the same effect as the underdogs of Marvel.
DC has plenty of underdog stories as well. For example, anti-hero Catwoman starts out as a simple cat burglar, trying to eke out a living amidst the madness of the city of Gotham. Barry Allen was just a police detective when, much like Peter Parker, a laboratory accident granted him amazing superpowers. Like Spider-Man, Allen's superhero persona, the Flash, often acts as a grounding, humanizing figure to his more powerful superhero colleagues. Furthermore, Marvel's roster may contain some average Joes, but it's also filled with extremely impressive figures that normal people can't relate to. Just look at how many rich geniuses there are, like Tony Stark, Bruce Banner, Reed Richards, and even Victor Von Doom. Or look at the Asgardian royalty, Thor and Loki, who are basically gods. And even when Marvel has a "normal" hero, it throws them into such outlandish circumstances, like the aforementioned multiverse plot, that the audience can no longer relate to them. It becomes a fantasy story with a different paint job. And at that point, if the story becomes so fantastic, why bother grounding your heroes in reality in the first place? Fantasy isn't a bad thing; audiences crave escapism. But if an audience wants to escape the real world for a bit, why would you remind them of it with an ordinary main character in the ordinary world? This is where DC's godlike, larger-than-life heroes comes in, and fills a better role than those of Marvel.