>>280780710She is. It may be a tad confusing gauging the popularity of a character from an almost 20 (!) year-old TV show. Especially now, because the new "otaku" are fickle, disloyal and easily influenced by trends, so you won't get passionate, autistic followings like with Jesus Yamato or Haruhi anymore.
Despite all that, there are still some traces of her popularity, like the video for God Knows, or the fact that there are still Haruhi events in Japan from time to time (there's a SOS Brigade pop-up shop going around right now at Gee Stores nationwide).
Compare that to something like Ouran, that aired literally the same season and was fucking huge, not only in Japan but all around the world. When was the last time you heard someone talk about it?