What martial art is the most famous?
Statistically speaking you would have to research that. Karate
has been the traditional western word for martial arts in general.
Second to that would be Kung-Fu. Mostly both are used as slang for
martial arts in general but they are actual styles. This
generalization has led to the widespread knowledge and interest in
their knowledge as well as many Hollywood movies portraying their
use. The three top in America would be Karate, Taekwondo, and Judo