Ok, so I'm a day (or two, depending on the time zone)behind, but I'm surprised there hasn't been an exclusive list of favorite love songs.
It might be hard to pick one, but I'll mention 5 with one favorite video.
You Are the Sunshine of My Life—Stevie Wonder
http://www.youtube.com/watch?v=uPyq4iqt6Go&feature=kp
Through the Fire—Chaka Khan
Goin' Out of My Head—Luther Vandross
How 'Bout Us—Champaign
Overjoyed—Stevie Wonder