I would say, for Castlevania, Alucard is just as much of a mascot as the Belmont’s are.
I think some folks might be misconstruing the point.
Mascots/protagonists differ from series to series. It is not a “one size fits all” definition. For example, Alucard is an icon of Castlevania as a series and is a protagonist of arguably the most influential game in the series. That’s nothing to sneeze at.
Likewise, when it comes to Devil May Cry, Dante is essentially the pick. It’s Dante.
If we were to get a character from Nier, there’s two options: either the protagonist from the first game or 2B, from the arguably more “mainstream” title. In that case, 2B makes plenty of sense.
When it comes to ARMS? The difference is that the characters in discussion are just...not quite the same. Spring Man/Ribbon Girl are the mascots/cover characters. Min-Min is popular, but she’s not the mascot/cover girl. When it comes to gameplay, Spring Man is just as capable as embodying the gameplay of ARMS as Min-Min is. I’d actually argue that if it’s focusing on “ARMS” as a game rather than the specific character, Spring Man makes more sense in that regard because he’s basic, yet still unique from the rest of the Smash roster.
That said, I don’t think anybody should discount Min-Min as a contender simply based on her popularity. There’s no doubt that if they went for somebody aside from Spring Man and Ribbon Girl, Min-Min is looking good (though despite that, if popularity is a big indicator, why aren’t we talking more about Ninjara? Isn’t he popular?) She has merits to get in. I just don’t think popularity is the be all end all “thing” to get somebody into Smash, and am interested in discussing it further.
EDIT: Just to be clear, in my opinion ARMS is between Spring Man (cover boy, mascot) or Min-Min (popular).
I do wonder though, if somebody can answer for me, how does Ninjara compare to Min-Min in terms of popularity? I’ve heard he’s popular in his own right but wasn’t exactly sure how it compares.