https://db-engines.com/en/ranking/graph+dbms
As for standards, absolutely. Gremlin and TinkerPop are both common ways to interface with Graph Databases that work across many different vendors.
That said, IMHO graph databases are pretty niche. SQL took off because the ability to normalize data when you store it and then relate it as needed when you query while still getting great performance for large-ish data (thanks to indices and query optimizers) is really powerful.