The most famous tango singer in Argentina is Carlos Gardel. Although he was born in Toulouse, France, he has been the symbol of Argentina -and especially Buenos Aires- for the last 100 years. He is the benchmark for everything; if you are able to do something that people will admire, they will tell you that "you are Gardel". If you try to do something above your ability people will ask you if you think you are Gardel, and so on.
He died in 1935 so his figure is slowly fading and being replaced by football players, like Diego Maradona or, more recently, Messi. Anyway, he won't be replaced completely as he is loved by everyone, unlike football players who have plenty of detractors and will never have universal acceptance.