Of all the subjects in popular song, romantic love is bar far the most common. Partly for this reason, it's very difficult to write love songs that aren't cliche ridden, sentimental tripe or both. I can't seem to do it. The closest I seem to have come is "She Loves Me Still," which is more of a creepy stalker song. There's just no way a tune like that will get you laid.
It's a good thing I came across this absolutely awesome tutorial video on how to write a killer love song. Here's Australia's Axis of Awesome showing us how it is done. Enjoy.