Nintendo tries to appeal to everyone with each game, which is reflected in their high user score averages. There's something about Nintendo's design philosophy that makes all of their games fire the same synapses in the brain. Mario Kart and Smash Bros are in completely different genres, but they are equally approachable and fun. Nintendo's consistency makes it easy for people to confidently purchase a game of any genre and know that it will probably be enjoyable.
The overall perception of the PS4 and XBO is that they have plenty of great games- it's just that gamers don't always agree on which ones.
I looked at the top 10 games that people bought alongside a PS4 and Wii U on Amazon, and noted how many were first party:
Wii U
SNMB/Luigi U bundle: 7 of 10
3D World/NintendoLand bundle: 6 of 10
MK8/NintendoLand bundle: 6 of 10
32GB Deluxe: 9 of 10
Zelda Windwaker bundle: 9 of 10
PS4
White Destiny bundle: 2 of 10
Plain PS4: 1 of 10
GTAV/Last of Us bundle: 1 of 10
Dualshock 4 bundle: 0 of 10
Battlefield launch bundle: 2 of 10
500GB Last of Us bundle: 1 of 10
Instead of Sony published games, PS4 owners were most commonly buying Far Cry, Minecraft, Assassin's Creed, Destiny, Call of Duty, GTAV, Fifa, Middle Earth, Madden, and Need for Speed. Wii U owners were buying the games listed in the Nintendo graphic, no surprise, due to the reasons I listed above.
What I'm trying to say is that Metacritic user scores are more harsh on PS4 games because there is more trial and error because each game varies so much in design, making each PS4 software purchase a bit more risky than a tried and true Nintendo game.