One hit song / album does not make you NGG. NJ just debuted and we are yet to see their full potential.
NGG is a title given by the Korean public. I am unsure if it is official or not, but from what I know, the previous "NGGs" have had multiple hits and have made an impact in the industry that has earned them the title.
There is no doubt that there is a lot of potential in the girls as their debut has been a huge hit in terms of charting. But they have just debuted, they are less than a month old, so the korean gp needs time to get used to their image.
