We are all so used to Sigourney as Ripley at this point, but I wonder if ALIEN were made today that individuals would be up in arms about it.
I did a quick search for headshots of Sigourney in 1978, when they'd be casting for Alien. I doubt many people could see her playing the hardened Ripley from this glamour shot, which is similar to our new spread of actors:
Yet you throw them on a set with proper direction, wardrobe, propping and lighting and it changes the way a person looks. Here's Sigourney testing for ALIEN:
Sigourney still looks like a baby to me in these photos, even if she is pushing 30. But I'm me, have my own opinions and can be totally wrong in this observation.
But this is coming from someone who films and photographs people as his daily job, so also speaking from experiences.
The amount of times I thought someone was not correct for something until I got them in front of the camera is something I've lost track of.