"You Jackson? You look like Jackson..."
Your question is flawed, or at least to vague. What kind of fighting are you talking about? In a ring, with rules, etc? Out on the street? Weapons? etc.
Generally it boils down to the fighter. Certain styles are more condusive to teaching you to be a good fighter. Boxing, Muai Thai, are generally considered to be better striking arts than traditional Karate or Tai Kwon Do, but it is how the fighter applies the skill they have.
Look at the UFC/Pride champs, now they come from a variety of disciplines. Tito has a background in wrestling. Nogeria in pride is a Jiu Jitsu player. Sapp is just a big monster. No one style is best.