- World of Warcraft -> C++ / DirectX
- Guild Wars -> C++ / DirectX
- R.O.S.E
- FlyFF
- Maplestory
- Cabal
- Everquest II -> C++ / DirectX
I haven't played the others, but there's a good chance that they are all the same answer. C++ is the industry standard programming language (for commercial games), and DirectX is pretty much the standard for game development on Windows (again, primarily commercially).
So, just because all of the "big boys" use C++/DirectX don't feel obligated to yourself. Commercial games and hobby games are two very different realms. There's tons of languages/libraries that can do virtually anything a hobbyist developer can pump out. Check out the "Big List" sticky (in Game Development) for some good engines/libs around.