This is false. Fire Emblem has scored 90+ for its last two major installments; Mario Kart scored a 90+ with its last major installment. Metroid Prime has not had a single sub-90 game yet.
Incidentally, if 'lower than 90' is an argument to be used against Nintendo, no Sony franchise counts. At all. The closest thing is Uncharted, but there, The Lost Legacy and Golden Abyss drag it down.
This is a really stupid argument to be making.
Metacritic Scores:
For PS4
Uncharted 4 is 93
Bloodborne is 92
For Nintendo 3DS
Fire Emblem Awakening is 92
The Legend of Zelda: A Link Between Worlds is 91
For Nintendo Switch
The Legend of Zelda: Breath of the Wild is 97
Super Mario Odyssey is 97
You say Fire Emblem has scored 90+ for its last two major installments... Are you sure?
Fire Emblem Warrior is 75
Fire Emblem Echoes: Shadows of Valentia is 81
Fire Emblem Fates: Conquest is 87
Fire Emblem Fates: Birthright is 86
You say Mario Kart scored 90+ with its last major installment... Hmm
Mario Kart 8 for the WIIU is 88
If you're thinking about the deluxe version of the game on Switch then you may as well add the Last of Us Remastered at 95 for Sony
You say Metroid Prime had not had a single sub-90 game yet... Okay
Metroid: Samus Returns is 86
Metroid Prime: Federation Force is 64
You say no Sony franchise counts is legitimate bait so I had to do the research for you. So I'm not sure who really is making the stupid argument and it's really comes across as condescending on your part...