I can´t believe this!!! Earlier this week I was about to post the EXACT SAME QUESTION!! I was going to ask if anyone knows where the Soup Nazi is hiding?
I too am looking for other places that serve good soups.
If you want to taste some GREAT SOUPS you should try Kansas, either in Palermo or Acassuso, northern suburbs. Also in Acassuso, only 3 blocks from Kansas is The Embers: they have great French Onion Soup, plus Chili ocn Carne. (Kansas does too)
Pauper is right. Unfortunately they brain-wash children here into believing that having their soup is a punishment, and just as with their fear for spices and flavor, they have no idea what they are missing.
The Natural Deli in Las Cañitas will often have a yummy soup of the day, and happily, it isn't always a squash soup, which is the most common savory liquid one finds in Buenos Aires. The restaurant is at Gorostiaga 1776. They bake their own breads as well, so you can get a nice healthy piece of nutty wheat bread with your soup.
(Since it's not a regular part of the menu, I would call and see if you like what they're serving: 4777-0372/0418.)