This thread prompted me to register.
I wanted to post "Brian's Song", but someone beat me to it. So I'll just second him.
I also saw "Marley and Me" listed. If you'll indulge me, I'll describe my experience with that movie.
I thought from the movie trailers and the first few minutes that it was just going to be a funny movie about a big, unintentionally destructive dog. As I watched the movie, I gradually realized that we were watching the development, growth, and aging of a family; and I became more and more convinced as the movie progressed that part of that development was going to be watching Marley die. Well, I didn't do it. I took my own dog out for a walk and skipped the last 10 or 15 minutes.
I'll put in a vote for "A Christmas Carol". It always warms my heart that Scrooge is able to rehabilitate himself and that others welcome the new him. Makes me think there's still hope for a misanthrope like me.