A thread like this has no choice but to devolve into like it/don't like it, love it/hate it.
The problem with Ridley's prequels is that he tired of his beast, grew bored with it. Maybe there really isn't anywhere left to go. The visual language is fleshed out, the nature of the Alien universe is known. Yet, there might be room for well-told stories there. The problem with Blomkamp's proposed Alien 5 might be that he is too in love with Aliens. To me, Ripley, Hicks and Newt should stay cold in their graves.
Ridley made his movies, and they are what they are. Blomkamp hasn't made his movie, but a lot of the concept art looked promising. This ADI piece is interesting. It seems pretty obvious that everyone involved with Blomkamp's proposal has great love for Giger's original design. I doubt a Blomkamp Alien(s) movie would be truly great, but I would have liked to see it.