With the exception of Sora, Geno has always been the most requested Square character within the fanbase. That's not new. But Nintendo clearly has prioritized going outside this small sliver for their selection, which is smart, and Square still has many characters which are less popular than Geno on a Smash poll but way more popular in general.
They may change their priorities, but this is really the same point it's always been. It was said before Cloud, it was said before Hero, and it was said before Sephiroth.
The thing is about this is that...well, are there REALLY that many characters that are more popular in general? This is why I see 2B being the only contender in this regard because Geno just keeps swelling to the point where everyone who talks Smash on social media has to bring him up regardless how they feel about him, but you really don't see this happening with other characters Square has outside of the ones we got in already.
Now sure, still kinda talking about Smash here, but I will get to general popularity...even though talking about the Ballot is much more important. Thinking upon the Ballot and how we know know that mock polls are at least in the ballpark for results so long as they aren't things like that Reddit one where the TF2 fans botted the poll, we can compare notes to get an idea of how well Cloud placed in the Ballot and by extension how Sephiroth and other beloved FF characters placed.
By Sakurai's own words, Cloud got the majority of the FF-related votes/requests, and Sakurai estimates it to be between a fourth and a third of all the FF votes/requests were for Cloud. This likely means Sakurai was stating that Cloud was the most-requested FF character, which make sense. However, if he got THAT MANY off the FF votes in the Ballot, this would suggest that every other FF character placed relatively low in comparison, just based on how fractions and dividing things up works. When you then consider that FF has many characters people love other than Cloud like Sephiroth, Terra, Noctis, Tidus, Yuna, Squall, Tifa, Black Mage, Lightning...the list goes on for a while, so you need to divide the other three-fourths to two-thirds of all of those votes between them all.
I would find it incredibly likely that Sephiroth was the second-most voted, but we don't know that for sure, but what we do know is that each of these characters likely placed low on the Ballot overall and that dragged Cloud down some as well. This isn't a situation where 90-100% of KH fans are voting for Sora (giving leeway for like 10% who may have wanted Riku instead): this is a longer-running franchise that has multiple protagonists, and Cloud got between 25 and 33.3% of all the FF votes. Logically, this means that fanbases who only support mostly one character could come out in slightly less or equal numbers and still get their character to have more votes than Cloud or any other FF character in the Ballot. When you factor in what you said about Sora being the only exception to Geno being the most requested Square character for Smash, it's just another factor that points to Geno doing a lot better in the Ballot than I think even Geno fans believe.
But, let's go to more public popular opinion.
It's true that Geno isn't as mainstream as other Square characters, this is just a fact of life when you are a one-off character from a franchise that had one game and then died because companies are stupid sometimes. Had things been different, he could easily be a much more popular character and maybe have already had crossovers in other Square franchises, but alas, here we are. Thus, there are many other Square characters more popular than Geno in the mainstream. Pretty sure every big character from Life Is Strange falls under this, as it's popular with the public for reasons I don't understand since I never touched the game. I'm sure nearly every FF protag and their party members are publicly more popular so long as they have staying power, and I know for a fact that 2B is massively popular for a whole bunch of reasons...but when people bring up Lara Croft or Neku, I feel like they aren't being entirely honest with their popularity.
Let's start with Crono. People really love Trigger and nobody ever talks about Cross, but the series has gotten nothing but ports for a very long time...much like SMRPG. Both of these characters come from a niche RPG series that have been dead for a while, and both of them are relatively popular now as cult classics due to the praise given to them by people who played them when they grew up mixed with a smaller amount of people playing them in current times, and they both have request to be in Smash for very similar reasons. I feel the only difference here is that here is Geno and SMRPG is just MORE of all of that in more recent times and has been much more than that in the Smash fandom for some time. If you would have asked me five or ten years ago if the public talks more about Chrono Trigger or SMRPG, I would have easily said Chrono Trigger...but it's not as clear cut as it used to be. It's for this reason I think Crono will likely get something in Smash eventually just like Geno, though I'm not sure what or when: it's the same situation, it's just that us Geno fans have been pushing harder for longer and that is having a clear affect.
Now for Neku. Hoo boy, people really try to hype up TWEWY but I did my research and it is incredibly niche. Now don't get me wrong, I'm a big advocate of 'sales figures don't mean everything, nor does it mean much at all' but if we are talking about general popularity then it does matter: if a game didn't sell very well, odds are it's not very popular or it's old and sales numbers were different. TWEWY was a DS game and was considered to be the best RPG on the DS and one of the greatest DS games, and yet the numbers I'm finding seem rather low: from what I can find (feel free to provide better sources if you find them) is that it sold around 200,000 units in Japan and about 140,000 in the US and 20,000 in Europe. These are numbers registered during the months following the games release in each country, so I'm sure the numbers are a bit higher than that overall
Now,
I KNOW that 2007/2008 and 1996 are completely different eras, but the DS was making Nintendo so much money it was ridiculous and basically EVERY KID had a DS. So, to only sell around that much seems a little strange, I guess it just wasn't all that popular. Contrast this with SMRPG that sold 1.47 million units in Japan and likely broke 500,000 units in the US while being the 6th highest selling SNES game that year and being the most-rented game (Yes, people used to rent games. It was Earlier Times back then.) for 14 weeks straight. I'll admit SMRPG had Mario to give it that push, for sure, but both of these games were seemingly setup for massive success and TWEWY just was not well-received by the public despite all it's accolades. The crazy thing is that it seems consistent with the series: NEO was super hyped up by TWEWY fans and yet while we have no official numbers, it did not do very well in it's opening week at all. It even had an anime to promote the game, which I've also seen people complaining that it was too rushed and suffers in quality and cutting out way too much of the story and character moments. This leads me to believe that TWEWY really isn't all that popular in the public gaming sphere and may be even more niche than Chrono Trigger/Cross or SMRPG.
And now, good ol' polygons herself, Lara Croft. She also debuted in 1996, funny that. Sure, the games were popular and probably fun to play, but she IS iconic for her booba and that is something that needs to be said. Now I know she wasn't popular only for that, but it definitely was a big part of it initially: she's a big booba sexy badass ***** who kicks ass, takes names, and does everything else Indiana Jones does but leaves young boys drooling in the process. I think she's dope and I also think she is a big part of gaming culture, whether people may view that for better or worse, but she definitely fell off massively in public popularity over the years until her big reboot in 2013. Before then the game sales were quite low and her franchise was in hibernation for five years, and now she comes back but she's next to nothing like what she used to be in terms of her design. The reboot was a massive success, like
MASSIVE success, but it seems like something happened with the next two installments because they tanked in sales in comparison. I
vaguely remember some sort of controversy over the most recent game in the series, but I have no idea what it was about. And now, history repeats itself with Lara having another 5-year hibernation with no new titles.
Contrast all of this with 2B, who has been getting nothing but new games on lots of platforms and a buttload of crossovers in other popular media. Clearly, 2B dominates the space of public popularity for Square characters outside of merhaps someone from Life Is Strange. This is why I find her to be a serious contender for Geno in terms of who gets into the next Smash game from Square.
I'll end this portion of discussion with a single image that wrecks the argument of public popularity being a sole major factor.
It's part of the process, but not the most important to be sure. It matter more for DLC than it does for the main game as well, and I think Geno could get in a base game when you look at how much content from SMRPG got into base Ultimate, so Geno not being that big in the public eye doesn't really stop him at all.
I could see Square getting hit upside the head with the Capcom in Ultimate stick for the next game and just not getting a new character.
For one, it'll be hard to bring back Cloud, Sephiroth, Hero, and Sora. I'd be willing to be at least 2 of the 4, if not all 4, are DLC assuming we don't get a miraculous "Everyone is Here...2!"
For another, Square Enix has four unique characters, which is the most of any third party company. As much as the sentiment failed during Ultimate Speculation, I feel like we're due for a couple of other companies (cough Capcom cough) to get representation before we revisit Square's library.
I disagree entirely, because while Capcom does have a big list it tends to end up mostly being within the same franchise that they have already heavily represented, which is why the only big contenders for Capcom are DMC and Ace Attorney. Monster Hunter is big, but as I've said many times, the monster are what represents the series and not the hunters, and I feel as though RE could have a chance but it depends on how fun and unique of a moveset they can make when each playable character is just using a variety of firearms and a knife. Made the work in MvC though, so I have faith it could be done.
Also Square just makes too many beloved characters and Sakurai is friend with Nomura, so I doubt they will miss out in the next title.