This is one of the most important question to ask while building and testing products and designing services(great ones).
Look around you. All the products, movies, concepts, services you admire and adore are the ones which hooked you like anything when you saw/used them. They captured your imagination. Be it Apple’s iphone, Amazon’s customer service, Google glass or anything else. Did it spellbound you?
This can be one of the central traits for user testing around which everything revolves. Ultimately, you want your product to delight your users, fulfill that need in a manner which no one else has not been able to.