That Victory sign has been around way longer than Mario. I've seen a picture of Winston Chuchill with the Victory sign. Back then, it had to have stood for Victory. Then, sometime around the 60's, that 'V' sign became popular among the 'Hippies', who used it as a sign of Peace to protest against the Vietnam War. Finally, a Japanese video game company (not 100% sure when Mario first started his victory pose with the 'V' sign) decided to make a sprite of their mascot flashing that sign. Thus, the "V for Victory" sign became popular among gamers.