There are some homebrew packages you can download to develop for these consoles (Xbox and PS2 anyway), but you must have a development or debug kit (available only from the manufacturer if you are a registered developer and cost mucho $$$, in which case you have the official SDK anyway), or a hacked console (modchip installed). The official SDKs are all in C and C++ and the unofficial SDKs are all in C and C++. GameCube requires special hardware, once again only available from Nintendo.