Given the simplicity of 3DGS's scripting language, it doesn't really have a rival (and if the stats I know about that someone told me about a few years ago are still true today, this is one of the reasons why 3DGS is the #1 selling game engine by a wide margin). Anything that requires you to know C++, C#, or "regular" language to use the engine is automatically disqualified. I and others like me couldn't use them, but we can use c-script, and Lite-C is close enough to c-script that it's still the simplest of all the scripting languages available in any engine.