[randomdude402]

I guess clear market winner depends on what one defines as market.

Anecdotally though, I have been working with medium sized startups in NYC that are heavily API driven for the last several years, and I haven't seen graphQL in production once. Not at my companies, nor in any external API we have interfaced with.

I will even go a step farther and day that I cannot recall a single time that another of the several dozens of devs or managers I have worked with has even mentioned the idea of using it.

I can only assume the market OP is referring to is a very specific one. I could make a guess or two, but wouldn't want to ruin the reader's enjoyment from doing the same.