I've said something similar to this somewhere else, but I cannot remember where it is. However, I feel that most fans of literature, movies, television, etc...are accustomed and rather demand to have the good guys win in the end. Had Sam and Frodo not survived people would generally leave the book feeling a bit empty.
I personally would like to see a bit more realism in killing off the main characters on occasion. Often we see secondary characters dies ie Theoden, Boromir etc... however the author is reluctant to kill the main character because of the public's view. The Silmarillion
might be an exception to this for Tolkien but then the question would be raised: Who is the main character? Morgoth? He didn't die. The silmarils? They didn't 'die' though two were lost. Feanor is not the 'main character' per se as the story isn't about him and his deeds rather the quest of the Simlarils, which he happened to create.
I found the previous post
here. I'm not sure how applicable it is but I think it is of merit.