I'm dating myself here, with my choice of group's and the song is more recent, but my favorite is the one that my wife and I call "our" song.

When You Love a Woman by Journey.

They were much more popular in the mid-late 80's than when they did this song back in 1997, but its words happen to fit our situation almost perfectly.

Also along this line is romantic music by Jim Brickman..most of his is instrumental, but it sets the mood very well.