I got Machoke. I'll admit, it's a good fit.
People don't understand the difference between explanation and justification, just because there's a reason behind something (and there's always a reason, Sakurai isn't an animal) doesn't mean the reason's valid. Saying Pokémon's selection makes sense because of marketing ignores the fact that doing something because it's profitable doesn't mean it'll be good, it's just putting on producer goggles and not looking at the actual grievance.
You know, I don't recall you using this argument for Zelda, double standard much?
I'd argue that's not necessarily the same thing either.
Mario, Pokemon, and Zelda, all three top Nintendo series, are
quite different in how their identities exist within media. All mainstream Mario games focus on Mario, just like every mainstream Zelda game focuses on Link, with a different cast of
supporting characters. Pokemon (which is also tied to trading cards, anime, among other merchandise) is different every single time, barring remakes, which is just like Fire Emblem. Both of those end up with different mascots or protagonists, which is something that Mario and Zelda do
not do. That point isn't really comparable.
Mario and Zelda, despite having shifting supporting cast members, are still quite different from one another. Mario itself is a series that spans genres. Supporting cast members like Rosalina end up in those games, as I assume Pauline also will. The Legend of Zelda does
not have that same structure to it. They come in one game, are gone the next.
This isn't even me saying that I think Midna, or Ghirahim, or Revali would be poor choices. I genuinely love the designs of characters from the Zelda series and enjoy the characters. I can't really speak for how Sakurai makes his decisions with Zelda either. But let's also not pretend as though Mario, Zelda, and Pokemon are all the same situations when it comes to the context of their characters and exposure/longevity of them.
If you ask me, the weakness of a Zelda character is that the focus goes from title to title. With Twilight Princess and Brawl, it was "Give Wolf Link and Midna!" Now that's hardly ever heard. Then it was Ghirahim, which now is practically non-existent. Then it was the Champions, and now that BOTW2 is coming, people have jumped to, "Give us a BOTW2 character!" There's no consistent support for any particular character. As it isn't a protagonist of a series with new casts every time (Pokemon, Fire Emblem) Zelda doesn't have that same "new protagonist" concept going for it. It inherently isn't like those two. The best way for that supporting Zelda character to get in is fan demand, but that fan demand isn't constant because it moves from game to game, never focusing.
At least, that's just my observation.