WhoDestroysTheGond
Ghost Manor for the 2600 is a fun game with lots of atmosphere. However it’s also pretty simple and will only occupy you for 10-20 minutes. It sure was a blast when I was a little kid, though.
There’s also Monster Bash, the 1982 Sega arcade game.
Ocarina of Time. After the action and increasingly beautiful pixel art of the first four Zelda games, I found the 3D one boring and ugly.
Like those occasional illustrations in Alice in Wonderland or Narnia, game manuals provided a window into a world you couldn’t fully see (in the case of old consoles, due to low res or low poly graphics) and served as a jumping off point for so many children’s imaginations to fill in the rest of the details.
Dadish
Wonder Boy 3: the Dragon’s Trap, a simple “Metroidvania” style platformer with fun action and enemy design. No deep story, but one of my all-time favorite game soundtracks
Thirty cents is an absolute steal. Evoland does well as an homage to multiple generations of CRPGs.
This doesn’t answer your question, but thank you for the love and patience you have for your son.
Ultima Runes of Virtue 1 & 2 for the Game Boy. Great action-adventure-puzzle games. But very unforgiving, every dungeon is filled with fatal errors. I couldn’t get to the end when I was young!