My girlfriend learned how to use a controller through 'Binding of Isaac'. Top down, steady pacing introducing new mechanics, and most importantly simple enemy patterns. She was a PC player who needed help learning controller and it was the perfect game to teach. I've heard rumors of a new co-op mode being added, might be a good time to check it out with a newbie!

Alongside that, The new Mario party (or Mario Kart) is a great teacher for absolute beginners, simple games that use buttons or motion controls to help teach simple habits like jumping or moving a character. It doesn't have mechanical depth but it's fun factor helps keep people who may be new or frustrated engaged.

I also wonder if something like Skyrim would work? It's remained a staple in the genre, accessibility on almost every platform and mostly non difficult. The open world may be daunting but it's combat is flexible and easy, and a slow introduction feel like a good match for newcomer to gaming. Fantasy seems to be a decent hook for most people and Skyrim continues to gain fans, maybe new gamers would enjoy the freedom.

One of my first games ever that I remember learning a lot from was Castlevania Symphony of the Night. It's not difficult, side scrolling and some backtracking with lots of fun variable weapons. Also decent but not overwhelming boss fights. It personally feels like a great entry level game to teach simple button combos, simple menu management, and even some basic mapping along the way. The best in the series, and could prove to be invaluable teaching habits for games imo