This is a terrible question, because it signifies that the guy has no personality of his own and is willing to change. The ultimate "nice guy" -- people pleasing while resentful inside. Trust me, I've been there.
It also kills the romantic tension and flirty atmosphere to ask the question at all. I'd say that the guy instead needs to say, "I'm me, this is what I stand for and I like. Tell me something I would never guess about yourself [or other interesting question about her reality, not her imagination]." Then, when she gives a thoughtful answer that appeals to him, he should applaud her for it and ask for a date.
I agree with your point that telling people what you want is not going to solve your dating problems. I'd also say that it's easy for me to think of lots of things I could want but maybe won't like when I get them. A better perspective is thinking about what I don't want, or what hasn't worked for me in the past, because the opposite of that is what I actually do want.