Zeph wins!
I love "A Thousand Years" by Christina Perri. It's probably one of my most favorite romantic songs that is out right now.
Also have to give a nod to "Here Without You" by 3 Doors Down and "Truly, Madly, Deeply" by Savage Garden since they both have meaning in Shinzuu and I's relationship.
But I'm just a sucker for romantic songs. If you named one (and I had heard of it), I'd probably say I love it.