Iguazu is a must! Do also the Brazilian side.
Im Buenos Aires, well, imagine its a small New York. Plenty of boutique shops, restaurants, clubs, etc etc.. thousands of them at a fraction of the cost.
what things do you enjoy? there is plenty to do. I am from Peru, but have been to Argentina twice and sale travel packages there. For some good ideas click on the link below:
www.argentinaforless.com
ps. have you been to Machu Piucchu? click below if not :)
www.peruforless.com