There are many foreign language threads around here. My children didn't like Rosetta Stone and didn't learn very much from the curriculum
I personally go with what holds interest for my children vs what is best language to pursue. Mine have done Italian, Spanish and sign language so far.
As far as economic value, I wish all my kids would do Spanish because here being bilingual in Spanish greatly improves your salary in many industries.
But I still go with what they are interested in.