There may be 50 ways to leave your lover, but there are 10 million ways to tell them you'll be sticking around. That's why paring down a Grand Canyon-size list of great love songs seemed impossible until we established some rules, which disqualify the wish-you-were-mine songs, the wow-you-look-hot-in-those-pants songs, and so many others that are not truly about L-O-V-E. (A few classics transcend our parameters — Whitney, you can thank us later.) We also limited standards, since otherwise they'd dominate. As for the rest...what can we say? Every time we hear them, our little hearts go pitter-pat...