I also dont understand all the "it is/it isnt" comments, not least from Ridley Scott himself. Even if the actual Zenomorph/Adult stage creature/call it what you will, is not in it (and im kinda hoping its not, in a way), this is undeniably an Alien film. With so many elements in it from the first film, i dont see how it couldnt be. If Ridley wants to create some kind of distance or room to maneuver, from the Alien universe, thats all well and good, and certainly by (seemingly) focusing on the Space Jockeys, he's exploring a unused story strand from the franchise, but this is clearly an "Alien" film.
Above any other film of 2012, this is the one for me.