Something to ponder:

So, I was reading a great blog today, and I came across a question I am not able to currently answer. Well, I could give an impulse answer, but after thinking further, I am not sure, so I'm gonna post it here, and ponder for a few days. I would love some feedback, but think about this for a little while.
Ok, here's the question: Out of all the movies you can think of, what is one movie that may never get a sequel, but you think deserves one?
Now, everyone can think of tons of their favorite movies they would love to see more of. I mean, look at my favorite movies list, all of those, I would love to see more of. Here is where it gets interesting. Knowing Hollywood's lack of ability to successfully execute a sequel (with few exceptions, we'll get into that later) would you really risk one of your favorite movies being completely ruined and that great memory and those characters you love being taken out? Now, you are starting to question some of those movies, aren't you?
So, originally, my first response was Serenity. As most of you know, it's one of my favorites. I also have a great story in mind for the movie. However, without a crazy amount of care, the characters I love so much would be irrevocably tarnished.