[Katsunami]

There is one thing that determines if you will become a bestseller or not, and that is: Does the editor/agent think you fit within the current taste of the masses, and if so, is it actually the case?

When doing sports, such as running, it can readily be determined if one is better than the other, because the better runner is faster all or most of the time. In chess, the stronger player will win more games.

Taste, opinion or 'current market trends' do not play any role in sports. You are better/stronger than others, and that can be determined without ail. They do, however, play major goals in the arts, such as painting, writing, or photography, and being 'better' is often in the eye of the beholder.

Look at E.L. James, with her Shades of Grey trilogy. It sells even better than Harry Potter, and she's the top earning author (at least, last time I saw a list of that, a year ago, with her earning around 91 million), even though many 'serious readers' bash the books without end.

Is E.L. James a bestseller? Yes, she sells a lot, obviously.
Is E.L. James a good author? Yes, or no, depending on whom you're asking...