I prefer to see good-ass writing. I don't care if it's about Living Lightning or barbecue or Meteor Man or spelunking or dental floss or how your girlfriend dumped you or Scarlet Witch. If the writing is GOOD, it will demand to be read. Go with your strengths as a writer. If an editor believes in your abilities, they'll work with you to widen your sweet spot and help you tell stories in new genres.

(just kidding about Scarlet Witch, though. I would NEVER read a Scarlet Witch story.)