CryptoKitties are cool. Art NFTs not so much. With art NFTs all you get is bragging rights that you bought X from Y. A CryptoKitty on the other hand actually has utility; not only in the game itself but also in other apps that are using them, e.g. HyperDragons eating CryptoKitties to grow stronger.

I think that's the only (if any) viable future for NFTs. A unique set of items or objects on the blockchain that follow a standard, making them interoperable between different apps. Since the blockchain is an open API by nature no-one can prevent you from building your own game utilizing the same NFTs. So when you buy a sword you can use it in all games that support it or, as in the case of HyperDragons, sacrifice it to get something else.