By far, the best customer need is one that he/she recognizes or perceives. This is the case because educating the marketplace is usually an expensive endeavor. A need can go unrecognized for many reasons; not the least common of which is that a solution to the customer's problem is considered to be impossible and people generally try not to need the impossible.
It is important that the recognized need be a customer's need, not the need of a non-customer, e.g., a government regulator or a person with no money. Recognized needs are usually easy to spot - if you offer to sell a customer a hypothetical product and he/she agrees to buy it, you can be assured that the need is recognized.
If the need for your invention is unrecognized, consider why that the case and what could be done about it.