The new Apple TV supports game controllers which is great. What's not so great is the fact that developers can't require them. By not allowing developers to require a game controller, what Apple have done is limited the platform and the games produced for it. I bought a Nimbus controller so I could play games like Rayman Adventures and Asphalt 8 but I only ever use 1 or 2 buttons on the controller in any given game. It's unreasonable to expect developers to have one set of controls for the Siri remote and another for a controller, without changing the game significantly to support this.
Guitar Hero, however, is allowed to require a controller but not a standard MFi controller; Guitar Hero requires a purpose-built controller that presumably won't be able to be used for other games on Apple TV (except more Guitar Hero games). This kind of double standard is frustrating for both developers and owners of the Apple TV and I hope Apple decide to reverse their decision on not requiring game controllers soon.