It would have to be a very deep, dedicated, selfless love to stay with a partner who you knew would not be spending intimate time with you. Almost nun or monk-like.
We are sexual beings, humans are, and I don't believe we can live without enjoying sex, or at the very least, closeness. Sex isn't just for making babies anymore, after all, it IS the 21st century and we've changed as a species so that sex is an essential form of expression now, especially toward a love partner.
Anyone who stayed with a person who prefered not to have sex for the rest of their life should be nominated for sainthood OR ... there should be an understanding that intimacy will be acquired elsewhere, from time to time.
I personally would feel uncomfortable balancing a halo on my head.
As the question has been put - "you know he is the right guy but..."
The question itself is quixotic - I'm not sure they'd be the right one if the sex wasn't right.
Speaking as a man (and getting ready to duck anyone throwing rotten veggies at me for my reply)...sexual compatibility is important to me in a relationship - it's the physical embodiment of my emotional self during lovemaking.
To be unable to express or enjoy that would be frustrating, at best.
I would express my feelings and give someone every opportunity to see if the cause of the...lack of desire...could be remedied.
In the end - it would all come down to how much I cared for the person. All relationships involve sacrifice of some type.