It's official: Prometheus is rated R for “sci-fi violence, including some intense images, and brief language.” I believe this is good news, and I'll tell you why:
The director's vision. While I think the rating system is generally a good thing - you really don't want your local municipalities rating and banning movies, believe me - it can get into these stupid grey areas. The rating for Prometheus sounds actually like sort of a softer R; there's no nudity specified and the violence is 'sci-fi violence,' which in MPAA speak usually means something different from gory violence (it probably means killing aliens and gooey, gross but not bloody stuff). It probably would have been simple to trim scenes to get a PG-13.
But what I want to see in Prometheus is Ridley Scott's movie. If he wants a scene to be intense, I want it to be intense, not homogenized to get a wider rating. I have heard about some of the 'intense' moments in this film, and if they work as well on screen as they do in the telling, they'll be powerful moments. I didn't want that power diluted in an attempt to add a few million to the gross by appealing to a younger audience.
On top of that, the Alien films - of which Prometheus is a part - are R-rated movies. The concept is inherently R-rated. It feels chickenshit to downplay that now, and I'm glad that Fox stuck by their guns and didn't water the concepts down. I guess you could do a PG-13 Alien, but what sort of asshole would want that?
Alien always has been for adults, and I'm excited that Prometheus will be as well.