What current gen game would you introduce a first time gamer to?

The Witness is a good answer.

Until Dawn was a big hit with less gaming focused friends; Life is Stange also.

Resogun is also a really good arcade-type intro for people but it's hard.

My ex and I really only bonded over games when we finally played Dynasty Warriors 7 together. She would like watching before then, but it was easy for her to play and get used to the dual analogue controls since she only played SNES games as a kid before.
I'm reminded of the Extra Credits episode of Gaming Literacy, in that it's near impossible to suggest works that get illiterate/new people into the medium because games are built on design foundations without necessarily any extensive thought into how newcomers will view those design conventions from an outsiders' perspective, versus other mediums where there's a better understanding of different demographics' thresholds for certain works and thus it's much easier to design for the sake of learning.

If you sat me with a person who had never touched a video game in their life but had infinite passion to learn, I'd want to go in stages. To get a person used to understanding a controller's function and relation to on-screen actions, either Tetris, Pong, or Breakout-- games with easily-understood rules and they only rely on a button press and/or basic movement along a single axis.

After that, probably Super Mario Bros. Two action buttons and two-axis movement, but now you're out of a closed space and have to contend with a variety of enemies and obstacles. World 1-1 in general is excessively good at teaching the player the rules of its gaming universe- jumping, how blocks work, that coins can telegraph certain actions, power-ups, etc.- without being overly punishing.

Perhaps between these two stages if necessary I'd insert Pac-Man, simply because it introduces you to what is effectively a single enemy, beneficiary items, and power-ups within a more controlled environment than in Super Mario Bros.

If you master these, I feel you can 3D game more easily than direct newcomers jumping in. Just about any kart/arcade racer (that's not F Zero GX) would serve a similar purpose as Pac Man without involving a person to deal with the sim aspects of more advanced titles, as they maintain simple rules, opponents, and inputs while ultimately getting the player to understand how to navigate a virtual 3D world. However, ones with a time attack option that disables opponents would be the best as you would be able to contend with the challenge of navigation without the stress of competition.

After that, you can move on to 3D movement with a character. Hands down the title for learning this is Super Mario 64. Granular movement and camera controls are introduced on top of the previous lessons, and you have the freedom to get used to these and Mario's plethora of jumping controls at your leisure in the castle courtyard before you ever tackle a level.

If you master these games, I feel the sky's the limit, and from there any player would have enough basic gaming literacy skills to go on and seek out more titles based upon their preferred tastes and build up more skills and knowledge that might be more specific to certain genres and conventions.
Why has no one mentioned Rocket League!? Like wtf!

Rocket League
Steer a car with 1 stick, make car go with a trigger, try to get ball in goal. It's easy to learn, and it's fun as hell.

Minecraft is also acceptable but rocket league is easier to grasp.

EDIT: I see one person actually mentioned it but didn't lead off with it.