What martial arts are most effective in a street fight?

The answer to this question would depend on the skill level of the practitioner. Western Boxing is considered by many to be the ultimate fighting science in the use of the closed fist. It has been studied by many Martial Arts masters. Many of whom have included it in their styles such as Fred Villari and Bruce Lee. A skilled boxer can be exceedingly effective and deliver devastating damage with it's combination of punches and footwork. Boxers however are limited to hand strikes alone. Martial Artists may employ the use of kicks, take-downs as well as grappling maneuvers to defeat their opponent. So if two opponents met with equal boxing skills, the addition of other martial skills could give him the advantage. That being said, a man with superior boxing skills can put a quick end to any confrontation before the use of any additional skills come into play.

There are many other martial arts that have far better hand skills than boxing. so i believe the answer wouldn't be boxing. boxing is a very brutal sport but it cant be considered a martial art.