I think you can easily compare the movie to 'Titanic'. Rich girl falls in love with the tramp. The parents disapprove. Another man shows up or is chosen by the parents and is good enough for the girl. So far, the storylines are pretty similar. Where the difference, you ask? Cal, Rose's fiance, didn't love her. He just wanted her because of her money. He was abusive and when Rose 'ran away' with Jack, his biggest concern was that he had lost the diamond 'the heart of the sea'
Allie's fiance did love her. Yes, he was rich, but that doesn't mean he was a bad person. When he found out about Noah he didn't get angry, he was just sad. And he let her go. That was a selfless action, because if you love someone you let them go, if you know there's someone else.

^ So agree Ellen.
Your comment made me want to watch both 'The Notebook' and 'Titanic' agaiin.
..I just can get his feeling. I know how it is to be someone's second choice and I really don't want to imagine how it is to let someone you truly love go. He's such a strong man.