How about the "other" love song. Not about breakups or lost loves, but the love that is not returned.

My first choice would be a beautiful love song that most people may not think of as unrequited. 

"Cherish" - The Association

 https://www.youtube.com/watch?v=bCfKvuh_uq8

Cherish is the word I use to describe
All the feeling that I have hiding here for you inside
You don't know how many times I've wished that I had told you
You don't know how many times I've wished that I could hold you
You don't know how many times I've wished that I could mold you
Into someone who could cherish me as much as I cherish you