The point of the movie wasn't Quasimodo getting the girl, it was about freeing Paris from Frollo's tyranny. The movie had Quasi being led away by a cheering crowd after getting an accepting hug from a little girl. It was literally one of Disney's most uplifting endings.

Sorry, I'm a Hunchback geek. It is my favorite Disney movie and I get really defensive about it since it's never grouped in with the modern "Classics" like Mermaid, Beast, Aladdin or Lion. It most assuredley had a happy ending as it drove purist fans of Victor Hugo's novel bonkers. A better example of a sad Disney ending is Pochahontas. It's too bad the rest of that movie sucked.