Ima just throw a few out I guess,

• "Portal"/"Portal 2"
• "Firewatch" is really good for a basic mostly walking/story based game. It would be great for a true beginner.
• "A Hat in Time" is a fantastic 3d platformer if you've ever played Mario 64 or Banjo Kazooie
• "A Short Hike"
• "Valheim" is a time sink but truly just an amazingly enjoyable game(Kinda hard for a true beginner)
• If you do ever want to try a game with him or ever have the time, "We Were Here" is a really fun co-op puzzle game series that I personally enjoyed a lot
• "Wildermyth" is a fun D&D style of game whilst I have only played multiplayer, it is single-player if you are into that kind of thing

These next few might get into the "harder"(by harder, I mostly mean more "complex" before all you shitlords come screaming about how these games are easy) section for someone completely new to games but if you want to learn, here they are:

• "Bioshock" series
• "Half-Life" series(dated but really fun)
• "Borderlands" series
• "Celeste" (Great but difficult even for life-long gamers)
• "Sid Meier's Civilization 6" If you like long "Risk" like games(Also DLC for it is def worth it)
• "Mirror's Edge" is fantastic and "Mirror's Edge Catalyst" is as well but Catalyst is open world so it might be easy to get lost
• "Risk of Rain 2" is fantastic but pretty darn tough
• "Outlast" is great if you like spooky games
• "Limbo" is a slower 2d platformer that I enjoyed
• "Seen" is kind of like "Limbo"
• "Little Nightmares"
• "Inside"
• "Ori and the Blind Forest"
• "Undertale"

I feel as if this should be more than enough to get your foot well past the door but as with all things, just because I enjoyed them doesn't mean you will or have so miss me with them fightin' words if you have any issues with this.