I’m afraid that might not be totally true. I love both C++ and C#, and I love both Unity and Unreal. But for me, C++ simply sucks for quick prototyping and gameplay scripting, and I would bet that’s why there was UnrealScript and now Blueprint in Unreal. Please note that in Unity, C# is used as both runtime and editor scripting language, and you will be amazed how easy C# could be used in both case for rapid prototyping and editor extension.
Have you guys checked out SkookumScript? It might not be as feature rich as C# but it’s born for game scripting, and quite promising.