XML vs YAML vs JSON for a 2D RPG [duplicate]

I would use the simplest thing that satisfies your requirements.

If you don't need hierarchical storage, then flat tabular files are so much easier to deal with than anything else. All you have to do is read lines off disk and split on tab.

If you are looking at more of key/value pair type storage (as opposed to lists of things), then INI files can be reasonable. This format has a lot of flexibility, though reasoning about it can less approachable when you start doing more complicated things than it was designed for.

If you need hierarchical, it's possible that JSON would be simpler. There are JSON libraries in wide range of languages, and it sounds like you already familiar.

https://stackoverflow.com/questions/245973/whats-the-best-c-json-parser

sqlite may be another option. There be dragons in SQL, but with a nice C++ wrapper around sqlite, it can be manageable. The primary benefit would be ACID, in my opinion.

The YAML spec looks somewhat lengthy, so I can guess that it has more kitchen sinks. Just skimming the libyaml docs, the API looks somewhat like SAX interfaces that I've used in the past. I have no a posteriori knowledge of it, but I would be reticent to start using it without a good reason.

XML sucks to deal with, don't opt in to it. There lots of reasons for this. I think the most relevant one in my mind is that it's prone to make the code that uses it more complicated than it would be otherwise. Any system I've seen designed with XML, reasoning about the XML is more complicated than the design interests that its trying to support. There are valid uses for it, though it's rare that another storage system wouldn't have been just as adequate.

Regardless of which one you choose, write as little code as you can managing it. You really want to write the classes your engine will use first. Then worry about serializing them. If you let your serialization influence your class design, you'll probably regret it. :)