I find the most difficult part of NPD is properly defining the problem. If that is wrong, all potential solutions will be wrong.
The next difficulty is making the subjective objective. At my current place of employment, we measure desirable by what we call the “excite-o-meter”. Yes, pretty stupid name but our folks in the field take it quite seriously and have developed methods to quantify a qualitative measure.
The outcome of an exciting solution to the right problem is simple, it is called sales. My last launched product in February hit $1MM/month in sales last month, technically making it the most desirable product our company has ever launched. But a different product (not mine) coming out in Feb 2018 is likely to crush those numbers. 