I think that an Alien 5 should be made to end the entire series once and for all. I love the series itself, but there is such a thing as "too much of a good thing." The fifth movie, i think, should take place primarily in space/on the alien homeworld, and then the xenomorphs should be destroyed once and for all. Personally, I think that a prequel to Alien would be completely farfetched, and not a very constructive idea. It would be a good idea to show the space jockeys in this film, and show how they got the xenomorphs in the first place, but I don't think the entire film should center around them. Ripley shouldn't be involved because she isn't Ripley anymore, but just a clone/alien hybrid. Instead, an entirely new cast should be used, but should mention past encounters of the xenomorphs. This would be a decent way to end the series, and if done, should only be left in the hands of Ridley Scott and/or James Cameron.