The people Who said Brazil, are correct. It has the most tourists in South America. One of my Uncle and his Family live in Brazil. And they have a very big population, as well as very popular promotion/tourism methods. So the people that answered You, before myself, are correct.

Brazil because it's the biggest. But Chile, Argentina, Colombia have many tourists as well.

According to the International Tourism agency, it is Brazil even without the World Cup.

Brazil

Right now, I would bet on Brazil.