I have the perfect guy, but I'm not attracted to him

I'm in a long-distance relationship with my ideal man, but I'm not as attracted to him as I should be. Everything else is perfect about him, but I find myself lusting over more attractive men. The next step is marriage, but I want to marry someone who I can wake up to and fall in love with all over again. However, I also don't want to throw away a great relationship over what might just be lust. Am I asking for too much in the "perfect guy"? Is there such a thing? Am I truly in love?