A year is a growing relationship and as you are aware, there is so much more to a relationship than looks. Relationships have to grow, be nutured and given space also. It's important to always maintain your individuality, friends and time for just yourself.
If he is good hearted, kind, considerate and will go that extra step for you, then you have a gem that is so hard to find now a days. If he is worthy to be valued beyond looks, treasure what you have, if you are just not feeling it then it's time to let him go and let him find someone who will value him for whom he is. Good luck.
It is normal in most relationships for the initial buzz and infatuation to die down, and a year in is pretty typical for this. If all else is good, and you suggest it is, then it's worth persevering. Turning that initial first-year excitement into something that is a bit slower, and steadier, but is stronger and long-lasting, that's the challenge you have now.
If you hope for that initial buzz to last indefinitely, you're in danger of never having a long-term relationship that makes it much beyond a year. Doesn't work like that, except in books and movies. Too many people seem to think it should, and too many good relationships fail because of unrealistic expectations, or simply because one/both participants want a hit of that high they get from a shiny new relationship, rather than working on maintaining and building the one they've got.
Good luck, I hope this works out good for you long-term.
Usually relationships are like the tides, they ebb and flow. How is the rest of the relationship? If all is fine there, I would ride it out a while and see where it goes. If there are other problems in the relationship, you could be reacting sub consciously to that and not even realize it. Or it could simply be that you are not as compatible as you thought you were and he is not the ONE and your losing interest? I would spend some time reflecting on your relationship and long term goals, see if you both have the same dreams and the same path of fulfilling them. If your desire is fading just for him but you feel attracted to others, that may be a clue that it is the relationship and not you.