As a straight guy, I consider men “attractive” when hmm, I’m not sure, but it’s a combination of handsomeness and more importantly, something about being strong in who and how they are, not a sexual thing, so they don’t need to be young, fit, erotic, or sexual. It’s more like who do I respect as a strong intelligent emotionally healthy man, align with at some level, and relate to their character as a strong character model. It’s a list culled by the short list of science fiction films I particularly like (and maybe my memory), so:
Harrison Ford
Sean Connery
Alec Guinness
Peter Cushing
Christopher Lee
Max von Sydow
Tom Baker
Martin Landau
Charlton Heston
William Shatner
David Tennant
Tom Skerritt
There’s a strong similar factor at play for me with women/characters as well. I’m attracted to personal strength of character, intelligence, emotional health, sympatheticness, and personal likability, that influences how I respond to their physical attractiveness. So, let’s see…
One of my first and few crushes on an actress/character was when I was a little kid, on Barbara Bain in Space 1999.
Being attractive is sort of a Hollywood requirement for most female actresses, so trying to just think who I find particularly personally attractive from sci-fi actresses I can think of, um… harder to think of than I expected.
Diana Rigg (if you can count her as sci fi by way of Cybernaut & other sci-fi-element episodes of The Avengers) is perhaps the best female example of what I mean in a character.
Kate Beckinsale (more attractive though when not in a dumb Underworld film)
Yvonne Craig more as just really pretty rather than given very strong characters (green-skinned Orion slave girl in a Start Trek mental ayslum, and Bat Girl, though I don’t consider comic book adaptations to be very sci fi), though I think the actress was a strong person, which comes through as attractive to me in her performances despite the limits of the roles.
The main actresses in Firefly were all pretty much strong attractive people:
Summer Glau
Morena Baccarin
Jewel Staite
Gina Torres