What is the best martial art/self-defense?

I hear Brazilian Jiu Jitsu and Krav Maga are superior.

there is no "best" martial art, though there are some fake/useless ones.  it also depends on why you would be taking it.. if you want it for competetive purposes then the effectivness in a real fight would be lower then a MA designed specifically for a real fight.  for instance, jiu-jitsu is good a one, in a ring.  on the street, chances are the guy will be armed and will have friends to back him up, so if you take the one down and keep him down, his buddies will be able to get all over you.  no MA is without flaws though, so find one you find which best fits with your body type and needs for taking it, rather then generalizing them all.