Well, it depends largely on the structure of the story, to be honest.
I have a superhero-storyworld that I occasionally poke at, where there are very few super-powered people - and both of my central "superhero"-characters are more the vigilante-variety. However, they are kept relevant in the story, because they have different priorities than the super-powered characters. They're the feet-on-the-ground, protect-our-streets kind of characters, and tend to deal with every-day tragedies - burning houses, violent robberies, murders, corrupt slum-lords, etc., - rather than the high-powered, save-the-world conflicts.
And that's an approach I think you can take even when your super-powered characters are central, and the non-powered ones are side-characters. Let them deal with the inevitable fallout of things. So your main character has a huge climactic battle with their enemies - and wrecks a lot of the surroundings in the process. Let your non-powered characters run around saving people from falling masonry, or organise the relief effort, or fight other non-powered people.
Or you can let them defeat super-powered people by use of their wits, underhanded trickery and/or specialised weapons. Strategy counts for a lot when it comes to fighting; it's hard even for super-powered people to block a hit they can't see coming.