"If you were accepted everywhere, which company will you choose?"
The best thing to do here not to say specifically which company you'd choose, or even which other companies you've applied to, but instead focus on how you'd choose among several offers. You can say that you'd consider all the aspects of each offer: salary, benefits, office culture, commute distance, potential for advancement, interesting projects, etc.; and that you'd choose the one that makes the most sense for you and your family. Be honest about the factors that you care about and what your priorities are — the recruiter may be asking in order to learn how to create an offer that you'll find compelling.
I'd avoid talking about the other places and positions to which you've applied. If they press you for that information, don't feel bad about deflecting with an answer like "I wouldn't have applied here unless I were really interested, so let's stick to talking about your company" or just "I'm not comfortable talking about that right now."
And how to answer when it's indeed you preferred one?
There really shouldn't be a difference between how you answer for the company you'd most like to work for and any other company. If you're not excited about the possibility of some position you've applied for, you probably shouldn't have applied in the first place.
This is a great opportunity to do all of the following:
Explain why you're interested in the job in question and what you like about the company.
Talk very briefly about what you think you can do for the company.
Say that you hope they're as interested in working with you as you are in working with them.