Market value varies by region. In some places it's Python, in others niche functional languages. Then of course JavaScript is everywhere and it doesn't hurt to at least know ES6 fundamentals.
Maybe have a look at spectrum.ieee.org/static/interactive-the-top-prog… and see if that helps?
Generally though I agree with Anuj that you should focus on concepts and not get hung up on language. eg. if you know OOP but haven't looked into FP yet, that's a big value add to consider. A lot of the highly-rated languages are FP-oriented.