The Wii's classic controller is supported on some games on Wii U such as Call of Duty Black Ops 2. You cannot use the Wii U Pro Controller or GamePad for Wii Games; this is because you must reboot your console to emulate your old Wii Menu. This is called Wii Mode. In Wii Mode, you still have 480p(upscaled to 1080p) max resolution and can only use Wii Controllers.