Like with anything else, depends on the games you want to make, and what you're comfortable learning. Besides, it's not just libraries but entire platforms. Libraries. Frameworks. Engines. Those are usually much more important than the language, and in fact might limit what languages you can use.
That said, if you're only just starting, consider Lua, and Love2D to go with it. It's a small language and a simple framework, which means a lot less to learn upfront than with other options.