Eh, personally I just look at the cruddy Wikipedia sales lists for each system to see if a game registers enough on the radar to be a potential candidate. RH and GS both had games that made it to the top sellers lists from what I could see, AW didn't.
Maybe I should start trying to figure out VGChart's layout and looking at that as well to further make awkward estimates as to which series should have priority over others or something. After all, it's Smash, and the sales of individual games at least didn't matter so much for 64 and Melee.
Obscure characters are boring, let's only add Mario characters.
Best case scenario
No joke, the only first party Nintendo characters that would still have enough influence to attract any new players are Mario spinoff fodder characters, with MAYYYBE Dixie Kong and Inkling thrown in there if we're being generous. Bandana Dee if we're being really, REALLY generous.
Anyone less well known than that is going to get blank stares from nearly anyone outside the direct Smash fandom, and that includes the likes of K. Rool and Ridley.
And while I'm at it, "anime" and "non-cartoony" characters thrive partially because some casuals who were initially lured in by more well known fare actually really like the same "anime" and "non-cartoony" designs that fans of more western looking series are repulsed by. It doesn't have anything to do with how well known they are, the designs alone do the work. Most requests that are typically made. . .don't quite get that benefit. Only really notable one I can think of that isn't over-repping a series even more or threatening to get a series accused of over-repping is Isaac, and his status as second party leaves him as a bit of a wild card considering second parties usually either get a flood of characters or no characters at all and Camelot in general has been getting Assist Trophies and songs but hasn't made the jump with anything they're in charge of.