NFT art is in the infant stages, and can be very volatile and risky. Don't purchase with the expectations of a return on investment. Could go up, could go down.
What makes them unique?
"CryptoKitties is a game centered around breedable, collectible, and oh-so-adorable creatures we call CryptoKitties! Each cat is one-of-a-kind and 100% owned by you; it cannot be replicated, taken away, or destroyed."
- Gamified collecting. Breed and discover new "cattributes"
- Random breeding outcomes created a large reseller market.
- One of the first NFT inspirations was the Crypto Kitties collection.
- On going game, that is interactive unlike most art.