Super Mario 64 is one of my go-tos. I just pop that original catridge in and Chewie...I'm home.
While nostalgia is definitely a powerful force, I actually believe Mario 64 still holds up. Its worlds, while defined by technical limitations at the time, feel perfectly stuffed without resorting to modern day open world bloat. The "one at a time" objectives are suited for pick-up-and-play sessions or long form speedruns. The sound direction is completely joy-filled. It's just an all-around classic.
That's probably why so many modders keep chasing it. That list includes Kaze Emanuar, who recently released a "Super Mario Sunshine 64" minihack out into the world. The gist: it re-captures the magic of Mario Sunshine (a more divisive entry) inside of the engine of Mario 64. If you're interested in the mod itself, it's listed in the description for the YouTube video.
For everyone else, you can watch the short debut video below or watch a lengthier 30-minute developer commentary.