I always wanted as many people as possible to read and enjoy my books. I write to appeal to a broad audience, and to give them an exciting and compelling story they won't want to put down. If I can do that, I've succeeded as a writer.
Keeping your reader's interest is the number one thing on my list. Sticking to the story and not going off on a tangent would be number two. Building in a satisfying conclusion, both to the story, and the character's journey arc would be my number three.