Adele is ruling the music business at the moment. Good luck to her. A big fish in a big pond. Other options are available of course. For instance, the big fish in the little pond, or the little fish in the little pond. And to be fair, you’re still a fish if you’re tiny and lost in the ocean.
But probably, if you’re a fish, the best thing is simply to focus on being the kind of fish that gets on with being fishy. Only anglers should really be worrying about how big that fish is and where it happens to be swimming.