Nintendo is a different beast. They have a dedicated audience that loves these games no matter what. They could almost live without any other games. So they rate these core games very highly, and people who are not into Nintendo games will not buy a Nintendo system to begin with, so there will be almost no bad ratings at all, except for third party games.
What about professional critics, then? I don't think they're pressured into anything per se, unless they want to avoid the wrath of notoriously passionate Nintendo fans. Also, Nintendo has a certain hip factor, so it's cool to at least pretend to like their games.
Sony and Microsoft games are mercilessly dragged through the mud, especially nowadays with all the political agendas flailing about. Scores will take a hit for those reasons alone, whereas it's more challenging to attach political gripes to Mario, Zelda or Animal Crossing or whatnot.







