Writer's Fallout Shelter

I have another question for you all...

I'm working on a novel that doesn't end well. I was wondering what people thought about that? For example, a lot of people didn't like the ending to the Fellowship of the Ring movie because it just had them walking off into the horizon and everyone else was scattered. So, it spawns my question:

What do you think of stories that end on a down note? I'm talking.... the main character dying, getting injured, failing, getting taken away, the antagonist winning, etc. Do you automatically hate them, think them a waste of time if they ended that way, shun the writer? Or do you think them realistic?

Help!