It compared surprisingly favourably. The C# engine was comparable (and regularly compared) to the Unreal Engine being used elsewhere in the company.

It was C# from the ground up. Scripting was provided via other .Net languages (Python in the case of the UI team).

Those are state of the art graphics gaming engines. It's quite hard to make e.g. an RTS using any of those. They are too FPS specific.

Command & Conquer is being built on Frostbite. [1]

[1] http://en.wikipedia.org/wiki/Command_%26_Conquer_(2013_video...