Street Fighter II originally had 8 playable World Warriors.
The original roster consisted of Ryu, Ken, E. Honda, Chun-Li, Blanka, Guile, Zangief, and Dhalsim. Ryu and Ken returned from the first Street Fighter, while the other six were new characters representing different countries, fighting styles, and character concepts. In the original arcade release, players selected one of these eight fighters and faced the others during the tournament.
The four remaining major fighters—Balrog, Vega, Sagat, and M. Bison—were CPU-controlled opponents known as the Grand Masters. They were not selectable in the original World Warrior version, which is why counting every fighter encountered in the game produces 12 rather than 8.
Later revisions expanded the playable roster. Champion Edition made the four bosses playable, bringing the total to 12, while Super Street Fighter II added four newcomers and raised the roster to 16. The answer therefore depends on the original version, but “original playable characters” correctly points to 8.