Epilogues

I'm not sure an epilogue will necessarily either save or ruin a film. Sometimes they work, like at the end of Goodfellers when you get a bit of text telling you what happened to the characters. Nice and simple. Then there's Bladerunner with a relatively appalling epilogue in the original version. Didn't ruin the film though.

I think they tagged the epilogue onto blade runner to make it more appealing to audiences. The directors cut ends with somewhat less of a happy end, I think it also makes it more explicit that harrison fords character was actually an android too.