So many good ones. Here are a few that have not been listed yet, I don't think. Some from my teen years, when romance is such a mystery--at least it was back then to me:
Sixteen Candles--The Crests
You Belong to Me--The Duprees
Ohh, Baby Baby--Smokey (or Linda...)
Most "romantic" video:
Jon Bon Jovi: Please Come Home for Christmas
(Eagles original version of this Charles Brown song is best recording, but when it comes to "romance"...)
And of course, before Led Zep IV, we all put on Johnny Mathis...did not matter which album; just make sure there is a big stack on the changer (remember them??).
Cheers!