I'm an OpenGL C++ programmer writing astronomy-physics simulators such as Kerbal. My website is photonbytes.com
I'm completely unfamiliar with commercialscripting languages.
I load my levels using a parser that can read a made up script in text files. Should I use c# or python instead of my own scripting language? I'm wondering if I'm missing out on some hidden benefit of python or c#. But at the same time I'm unsure due to my zero experience in the above two mentioned scripting languages if they can be used this way. My levels include the initial position and velocity of objects in Cartesian coordinates. Normally I just run my main.exe file from the compiler and it automatically looks fir the text file and reads line by line and interpret with my parser object. Is there an easier way to do this with c#/python?
C# is not a scripting language. Python is a well known and relatively easy to use language.
For a script language you need an interpreter though.
Whether you should use your own language depends on what do you want to do with it. Simple tasks you may do with your own. When it gets complex it is most likely better to use an existing language such as Python.
c# is much, much easier to make a simple windows GUI program in visual studio than c++ which pretty much forces you to choose between 1990s mode or 'microsoft's new language that isn't really c++' mode. This is by design: microsoft is pushing C#
python is really easy to tap libraries, but the core language is exceedingly slow. There are branches of the language that are a little better, but it still has a long way to go. Its claim to fame is ease of use.
c++ is fine for what you described. All 3 languages can do it, but if you have it working, no reason to redo it. You are not missing anything. C++ actually has a small edge here: there are a number of language creating tools in C and C++ that can be used for this, and c++ has a lot of roads into the gaming community which have libraries for scripting input files like LUA. A peer of mine used to use yacc/lex and friends (I forget the rest of the pieces) to make things like this, which is a big hammer for a little problem but it got it done efficiently.