I agree, but SFII was incremental improvement. It wasn't like it created the fighter genre. There were load of fighting games around before and during SFII hit the scene. Of course it was the most popular but the point i'm making is that, historically, it was nothing new.
But... it was. It's like trying to argue that Super Mario Brothers was nothing special because there were already a bunch of games where you controlled a guy and jumped on enemies. While it may have been derivative in some sense it was such a huge leap in sophistication that it turned a marginal genre into a huge craze.