Geno Boost, Grass, and IAmMetaKnight said no? Well, there goes my respect for those three.
Well, if you want to be technical, he was relevant in Ultra, which is pretty much Super Star on super steroids and is considered the superior and definitive version.
As for "popular, but not extremely popular," the same could be said for Roy, Lucas, all the Fire Emblem characters, Shulk, and most of the newcomers. In fact, that could even be used as a PRO-Bandanna Dee argument, because the less popular ones are the ones Sakurai seems to lean to, and the ones that some fans ask for, such as Isaac, Rundas (formerly), Geno (yes, I'm going there), Lip, and so on.
Once again, the same could be said for some of the characters in Smash right now, such as...pretty much every current DLC character. I will use Lucas as a fit for this template.
To someone who either didn't care for Lucas in Brawl or didn't play Mother 3, literally nothing would compel them to buy Lucas.
Unless you played the Japanese-exclusive Mother 3, chances were you had no idea who Lucas was, and with his game still being unknown to many, choosing to bring him back over someone like Wolf is a choice that to this day people are still questioning. Myself included.
I'll admit defeat here, because this was Lucas' sole purpose in Brawl.
Lucas really isn't a superstar when compared to like, 86% of Smash Bros.' cast.