Or? Spring Day is on the same level of Through the Night.
And there's also a whole Boy with Luv, which won 3 SOTY awards, same number as Gee and Cheer Up.
Like i said, chart perfomance is not everything there is to a hit song. Butter is doing better than Dynamite but i can assure you 100% that Dynamite is bigger in the US.
I think that Spring Day is a very popular song that appeals to a certain type of person, but it doesn't quite reach everyone in korea, which is for me the definition of national hit (entire generations dancing to it, hence the "national)
You dont have schools banning Spring Day like they did with LS, you dont have grandmas being taught the dance by their grandkids like that one Cheer Up video.
Then again, neither of us live in korea so we dont have a say on what is a national hit or not, its just assumptions