The thing I don't understand in all these discussion is I know a fair number of men in long term-- and sometimes happy-- relationships. They aren't high-display of masculinity guys, and yet, somehow they've hooked up with someone. How did they manage it?

From the "Perception Lab" at St Andrews:

Women’s preferences for men’s facial masculinity are especially interesting, as there is great variation in preferences across individuals. These preferences have been demonstrated to vary with age, womens’ own self-rated attractiveness, and across different phases of their menstrual cycle.

Older women tend to prefer more feminine faces. Women in the infertile part of their fertility cycle tend to prefer more feminine faces. Women rating themselves as less attractive tend to prefer more feminine faces.

By the way, I don't mean to imply that your guy friends in particular are in stable relationships because of these tendencies - I can think of many other reasons beyond the differing attractiveness of their faces, or their demeanour.