Wow, um...take a commercial game. Any one of 'em. Chances are, it was written in C++ or some variant. Dunno if that helps...
And if a game *wasn't* written in C++ or a variant of it, it most likely could be. Almost every game I've seen was C++ (the ones that tell you their programming language, anyway.)
DirectX is the graphics engine (I believe?) behind the game(s). Not sure on details, I just know it's a big graphics thing.
Hope it helped!