I don't think Alien 3 killed the franchise, if anything it kept it going. Personally I don't like it, it was a bizarre way of trying to end the series but then again nothing in life is so clear cut and conventional. When you think about it, Alien could have taken so many different routes but instead 20th Century Fox decided to take a comventional route and continued the story with Ripley and her battles with the Xenomorphs. One route that I suggested a while back and I believe must have been on the mind of Neill Blomkamp as well for a possible Alien 5 is Ripley, Newt and Hicks return to Earth and finally deal with not only the Xenomorph threat but the source of it: Weyland-Yutani. This would have been an even more cliche overdone theme basically closing the series with a bang. The only thing unconventional about this concept is that usually in a conclusion, the protagonists return to the source but in this case it is not a place, it was a little explained entity in Alien and Aliens where we find all the answers we needed.