All of the previously mentioned movies are great Valentine's movies.... I watch "P.S. I love you" and "Under the Tuscan Sun" and "Shirley Valentine" and not because of her last name being Valentine... hahahahaha but because it's a great love story.
The movie "Ghost" with Demi Moore
"The English Patient" with Ralph Fiennes aka Voldermort
"Casa Blanca" with Humphrey Bogart
"Say Anything" with John Cusack
"Notting Hill" with Hugh Grant
I know there are a ton more but these are my "Go To's" for romance... lol