Take Girl Genius. The mad scientist is a staple of superhero tales. But the Spark is the guiding principle of the world, and so steampunk.
Or Operation Chaos. A werewolf and a witch could be a feature of superhero tales. Especially a werewolf so little limited by the traditional problems of the type. But the world is too consistently magic and working on magical principles.
Even when you have a common initiating event or a meta-origin, the wild and woolly principles, running from sufficiently advanced technology to outright magic to slippery science, is part of the genre.
Meanwhile, I know my own superheroine walked into a cave or some such and touched a glowing gem. And I know one other superhero claims to have won his powers gambling, which is why they are so random. . . .
I may even decide not to give more origins.