Ah yes, Nintendo bias.
Random sampling of games developed by Nintendo, wholly owned subsidiaries, and external partners, from the west and the east, across genres, across the full score range, and across platformers. I'm sure there are scores both above and below the Metacritic that I've excluded, I literally just sorted by scores upwards and picked random stuff from platforms that Metacritic covers:
Pokemon Mystery Dungeon - Explorers of Time - 3 (MC 60) BELOW
Wario - Master of Disguise - 4 (MC 60) BELOW
Trace Memory R - 4 (MC 66) BELOW
Yoshi's Topsy-Turvy - 4 (MC 60) BELOW
Battalion Wars 2 - 5 (MC 75, bonus this is also a UK developer OMG BIAS) BELOW
DK King of Swing - 5 (MC 70) BELOW
Mario Kart Double Dash - 5 (MC 87--yes, they scored 37 points below the Metacritic average here) BELOW
Mario Strikers Charged - 6 (MC 79) BELOW
Excite Truck - 6 (MC 72) BELOW
Wario Land: Shake It - 6 (MC 78) BELOW
Hotel Dusk - 6 (MC 78) BELOW
Wii Sports Resort - 6 (MC 80) BELOW
Golden Sun - 7 (MC 91) BELOW
Tetris DS - 7 (MC 84) BELOW
New Super Mario Bros Wii - 7 (MC 87) BELOW
Drill Dozer - 7 (MC 81) BELOW
Professor Layton 1 - 7 (MC 85) BELOW
Paper Mario - 7 (MC 93) BELOW
DK Jungle Beat - 8 (MC 80) Exactly on Metacritic
Animal Crossing City Folk - 7 (MC 73) BELOW, but just one score bracket.
Punch-Out! - 8 (MC 86) BELOW, but just one score bracket
Minish Cap - 8 (MC 89) BELOW, but just one score bracket.
Twilight Princess - 9 (MC 95) BELOW, but just one score bracket.
Brawl - 9 (MC 93) BELOW, but just one score bracket.
M&L3 - Bowser's Inside Story - 9 (MC 90) Exactly on Metacritic
Super Mario Galaxy 2 - 10 (MC 97) FOUND IT! BIAS! HIGHER SCORE THAN METACRITIC! EDGE ALERT! ALERT! NINTENDO BIAS DETECTED! JOURNALISTIC SCANDAL! MONEYHATS! VENGEANCE AT LAST!!!!!
Edited with a second pass to fill out a few franchises that weren't represented in my original list.