I wish to develop a 3D game like x-plane, my question is that which environment/development-tool will provide me enough support? If i use XNA using C# then will it provide such a support that i can develop according to my desire? Will it also support high definition 3D terrain?

Or i have to start OpenGL and c++, although I find myself comfortable while programming using XNA.

Request for guidance towards right direction! Thanks!! 

I don't think using XNA is good idea.  It'll work, but if I remember correctly, it's a sort of 'dead' technology at this point.  OpenGL/C++ can do whatever you want it to do, but that's sort of the long way around.  And I mean the VERY long way around, as you'll be reinventing the wheel with almost every component of your game.  Maybe you want to do that (sometimes I want to do that), but you probably don't.  The standard engines to use for pretty much everything now are Unity and Unreal.  Just pick one and run with it.

9 hours ago, trjh2k2 said:

I don't think using XNA is good idea.  It'll work, but if I remember correctly, it's a sort of 'dead' technology at this point.  OpenGL/C++ can do whatever you want it to do, but that's sort of the long way around.  And I mean the VERY long way around, as you'll be reinventing the wheel with almost every component of your game.  Maybe you want to do that (sometimes I want to do that), but you probably don't.  The standard engines to use for pretty much everything now are Unity and Unreal.  Just pick one and run with it.

Yes, stay away from XNA and use something more up to date like Unity or Unreal. I believe XNA retired back in 2014 if I'm correct. I used it a lot back then, but haven't touched it since.

You can check out MonoGame - http://www.monogame.net/ it is a re-implementation of the XNA.

"MonoGame is an Open Source implementation of the Microsoft XNA 4 Framework. Our goal is to allow XNA developers on Xbox 360, Windows & Windows Phone to port their games to the iOS, Android, Mac OS X, Linux and Windows 8/10.As well as PlayStation Vita, Xbox One and PlayStation 4."