I think all 3 brands have their hardcore fans but amongst the hardcore fans, Nintendo hardcore fans are the most loyal.
1) Nintendo Direct videos have far higher view counts than the Playstation version. In fact, Nintendo related videos have a much higher number of views compared to Xbox and playstation. Just check the view counts of any switch or Nintendo game videos on YouTube.
Smash brothers tournaments often have way higher views than Street Fighter 5 and Tekken 7 tournaments, to the point that Smash is now the main game of Evo and not Street Fighter.
2) Do a poll for favourite character or games and the Nintendo character or game always exceeds the rest.
3) I haven't heard of playstation or Xbox evangelists. But I know a lot of switch evangelists in real life and on forums.
4) I know people who hate fighting games but bought Pokken and Smash Brothers Ultimate anyway because it has the Nintendo tag on it.
I'm going to make a bold prediction. If Dreams were made by Nintendo , it'd get lots of buzz and hype. But it's made by Sony. So it's going to sell like shit.
People who hate open world games suddenly love Breath Of The Wild. People who hate hack and slash games suddenly love Bayonetta or Astral Chain. The list goes on.
5) I also find that Nintendo fans often find the need to tell everyone that they are buying the switch version of a game. They can't simply say I'm buying XXX game. They'd have to add I'm buying XXX on the switch!!!
6) Also, the Media Create thread at resetera will not as be popular if switch isn't leading.
Nintendo related threads tend to have the most posts, be it vgchartz or resetera. Nintendo threads also have the most frequency.
7) Nintendo fans tend to tune out gaming news that are not Nintendo related. But the moment a game that wasn't on the switch suddenly comes to the switch, they'll be all over the news and excitedly telling everyone about it.
Lastly, I think there's nothing wrong with being a fan or being brand loyal as long as you're not hurting others. You're a human being. It's normal to be biased.
I like fanboys (as long as they are respectful and not over the top). They're passionate people who dare to admit they love and support something.
Those holier than thou people though who think they're so matured just because they aren't a fan of anything... Are hypocrites. They need to get off their high horse.
I also always doubt when people claim they own all consoles and are neutral. If you're a working adult, you don't have that luxury of time to play everything. Unless you're retired. Or very rich. I'm sure some of you genuinely own all 3 consoles. But I doubt it most of the time. It's just a front to make yourself look neutral (to strangers on the Internet).