I agree that it would be degrading to market a college based on this, but I'd also imagine that in an environment with a severe gender imbalance there would be people of the over-represented gender (of either gender) who would welcome the idea of a greater pool of potential partners in that environment (perhaps not enough to be willing to be "sold", as you've said).

> doubling the women/men ratio won't come close to doubling any particular guy's chances of having sex

While doubling the women/men ratio won't necessarily double any particular guy's chances of having sex, it will certainly increase it, and I'm certain you're familiar with the lengths people of either gender will go to to increase their chances of ending up in their ideal mating situation (straightforward sex or otherwise) by even a vanishingly or imaginarily tiny amount. And a favorable gender ratio won't effect a player's chances of having sex all that much, but for an average or socially-stunted guy, it will certainly increase his chances.

For one thing, a greater proportion of his interactions will be with women, increasing his chances by raw bayesian exposure, as well as by the greater socialization to women he will accrue. I do not reject the stereotype we all know, of guys who spend too much of their lives in environments with the opposite gender imbalance, as applicable in a large minority of cases; though I would be interested in hearing your experience and reasoning if you disagree.

As well, as rare in this environment, these men will be more individually valuable to women seeking male partners than they would otherwise be (for whatever benefits of a mating/partnership would apply to the people involved, and could be categorized as valuable). I don't think this concept of "value" would have as much of an effect on the difference in the situation as the 1st reason, but it would exist. The degree to which it would be multiplied from what it would be in a gender-neutral environment would still be dependent on each individual, and a clueless total loss would probably still not get laid or dated or tied-up and pooed on or whatever they're looking for, but it would absolutely make each more appealing to some degree. And (if you are willing to grant that confidence is sexy in many cases), any experience which increases a person's experience in and competence with sex and relationships feeds back on itself, and increases the likelihood of more experience.

So I think it would be pretty reasonable for most people to prefer a gender environment which is favourable to them. Of course, your expectation of the quality of an institution that would directly market itself based on this, and of the quality of the character of the people for whom this was not sufficiently distasteful to turn them away, might offset the benefits of the advertised gender environment. But having been an 18-year-old male and having known 18-year-old males, I do not think this is sufficient to nullify the appeal; and were this imbalance just known and not pimped, it would not be an entirely trivial factor in someone's choice of university.

NB: Pronoun "his" used for readability's sake, though if you'd judge what I've described to be equally applicable to women who are attracted to men in the reciprocal environment, substitute the gender-neutral pronoun of your choice. I also initially included gay women with the men above, but I suppose the dynamic is totally different for them -- the people you're attracted to are also your potential competition. Holy shit.