I fucking love Quest 64. I’m under no impression that it is a good game, but I grew up playing it and it remains one of my favorite comfort games to this day. I play through it fully once every year or two. I also enjoy other, better games, as have been mentioned elsewhere, but Quest is just special to me.
Just to say something beyond the obvious ones others are sharing; I really loved Battletanx. The game wasn’t all that great with the nostalgia goggles removed but I had so much fun playing it with friends 25 years ago
Superman: The New Superman Adventures (AKA Superman 64). It’s a baffling time capsule of poor management, crunched game development, and lack of coherent vision (mostly due to the management thing). Is flying through the rings tough? Yup. Do the missions make no sense? Yup. Is there a charm in firing it up and remembering to be grateful you’ve lived to yet another day where you can play Superman 64? Yup.