I personally think especially in Romantic movies when the guy doesn't get the girl and vice versa...it's a major blow it's like the whole film is about them getting to together and when they don't it just ruins the movie!!
But to list three I'd have to say.....
1 - Spanglish
2 - Becoming Jane
3 - Fellowship of the ring.....only because I wanted it to keep going...I didn't want to have to wait for the second and third.