these are the best ones:
you're the one- a thorn for every heart
still dreaming- silverstein
true romance- silverstein
with eyes wide shut- blessthefall (has a sad tune to it, but amazing love song)
other amazing ones:
comatose - skillet (there are so many ways to interpret this song, and one of them is love.. but its kinda sad so ya)
here without you- 3 doors down
stay tonight- matchbook romance
this i love - guns 'n' roses ( http://www.youtube.com/watch?v=uwTkAp-XeDU there are a lot of versions for this song from guns 'n' roses, but this one is the best in my opinion... and it has a sad tune to it, and he says "her"..)
your guardian angel- the red jumpsuit apparatus ( i hate the song but, its kind of about love)
if you are into songs that have some screamings, alesana has some amazing songs about love, but i didnt put their songs here because i dont think you'd want to put that for your bf/...
hope ive helped =D