Look, it's a bird! It's a plane! You know what, ready the arrows.
So..would someone like Superman be considered powerful in a world like D&D's, where magic is so readily available? Where even even a level one Wizard can cut past his usual defenses with a Magic Missile or Burning Hands? We're talking technical terms here, pretend somebody actually made a Kryptonian Player Character.
Note now, responses of how 'such a thing wouldn't be allowed at my table' doesn't really answer the question, here. Just sayin'.