I should point out again that the ballot performance for previously cut veterans is very weak evidence of future priority. For one, it doesn't tell us anything about how those characters measure up in popularity to the veterans which didn't get cut in 4.
But nor does it even really tell us Snake's current standing in the Smash community relative to Simon, now that Simon is in Smash. Even though Simon was at least eligible to be voted for on the ballot. Because the circumstances surrounding the ballot were basically optimal for cut veterans to perform well.
Tbh I'd actually be pretty shocked if Snake was prioritized more than Simon, but that's just me.
Obviously cut veterans performed exceptionally well in general because the fans are attached to characters already present in the game, but certain veterans performing better than others is pretty indicative of how well liked they are.
We know Bayonetta ranked above certain veterans, and we know in-turn that
Snake specifically was above Bayonetta overall. It'd be silly to say moveset wasn't a big part of that, ofc people will vote more for a fully unique character and series like Snake as opposed to asking for Pichu back, but I also think it's difficult to not acknowledge that a lot of the desire for Snake is because he's a beloved character from a beloved franchise. He's the character Everyone Is Here was built around who got the crowd cheers and the dramatic entrance.
In terms of specifically Snake vs Simon, I think the best indicator of that would probably just be playtime, in which case there's nothing but anecdotal evidence, but I would wager a decent guess that Snake is played more than the Belmonts.
Yeah, and I mean not to discredit Snake but I think generally seniority gives Smash characters an edge within the community. If you cut Jigglypuff now, people are gonna be upset right? But if you added Jigglypuff in Ultimate, and then cut her one game later... I think that'd be equivalent to cutting Plant, which most people are comfortable with. But if Plant was in 64... you get the picture. The "series staple" effect, a character's value is typically heightened by the fans if they were added in Brawl or earlier.
Snake is obviously a more popular character than these other examples of his own merit. He's the protagonist of a very successful series, so I'm not saying this popularity is exclusively founded in his role in Brawl. But I do think the mindset that breeds "[x] is more popular / has seniority" results in roster stagnation. I would be glad to welcome Snake back, but it would kind of suck to snip off a brand new series on the basis of seniority right (if it really had to come down to one)? The team seemed very excited to work with Castlevania, and the Metal Gear content was more or less the same from Brawl. So as far as series presence goes I get the impression that Castlevania may have a lot of room to grow.
Then again I probably wouldn't be so open to this "your turn" mentality toward like, cutting Mega Man, so I don't know. I just think we ought to be more fluid with guests, and we probably will have to be. I suppose since we lost Snake once before it's easier for me to accept losing him again.
I agree it's not good to prioritise legacy above all else, but I also think legacy being a pretty strong factor is understandable. Look at any other fighting game, I've brought this up before but Street Fighter 6's roster is built around a mix of entirely new characters and bringing back all the classic World Warriors who people are attached to and nostalgic for. Nostalgia might be a shallow reason, but it is a reason, and the fact that people might be attached to certain characters just because they're older doesn't change the fact that that attachment exists, I would say that applies to pretty much every fighting game. You need a healthy mix of newer characters and older ones.
But I think the bigger point is that I think Snake has way more going for him than just being a legacy character, and I'm not sure it makes sense to position it like he's tied too much into that even in the context of what you said about it not being exclusively founded in his Brawl role. Metal Gear is a massively popular and fondly remembered series which has just gotten a major revival, Snake is one of the most iconic and well-liked videogame protagonists. In a comparison between him and the Belmonts if you want to go that route, then Snake is I think undeniably the more popular character from a more popular series which is more important to its home company, and both now have major Nintendo releases. In the context of Smash itself, I would say that if anything the fact that Castlevania got so much content already means there's more you could do with Metal Gear getting a boost from its current legacy content. The only third-party series that significantly expanded in content going into Ultimate was Street Fighter, which was a DLC series, and I think that's more of an indication that the Smash team was less focused on expanding the content of the already included third party series overall. Even Mega Man's new assist trophies and cameos was just reusing the models already created for the trophies in Smash 4.
To be clear, I don't think it really has to be a "only one sticks around which is better" discussion, I'm only engaging more in that cause that's where the replies went, and my point overall was just that both of the Konami characters were really popular and seemed like they had a good shot of sticking around. I moreso I guess just want to say that I think sometimes the focus on retaining newer picks over legacy picks sometimes goes a bit far in the other direction I feel if that's the discussion, and doesn't necessarily recognise why some of the legacy characters have the attachment they do.
Though really, Snake has only been in two games and he was introduced in Brawl, I think he's only begun reaching the apex of Smash nostalgia recently lol.