Jack Johnson has some feel-good love songs that are romantic and goofy at the same time. Look into Bubble Toes, Banana Pancakes, Better Together, or Wrong Turn. These are just individual songs that came to me off the top of my head. His albums are all great for listening with a significant other.
Hawksley Workman has a fantastic song that I love to listen to with my girlfriend...it's called Future Language of Slaves, off Lover/Fighter. Also, off the same album, No Reason to Cry Your Eyes Out (On the Highway Tonight) is moving. In a more personal note for myself, I always find myself immensley moved by Safe and Sound, off For Him and the Girls.
Collective Soul has Under Heaven's Skies, Crown, Satellite, How Do You Love?, All, or Over Tokyo. The acoustic versions of some of these songs (found on From the Ground Up) are worthy of a spin.
And, for me, the quintissential love song, Aerosmith - I Don't Want to Miss a Thing.