It'd be painstaking reverse-engineering work, but I'm curious if more games in the future could have these sorts of "clean room" decompilations, provided the compiler toolchain can be realistically approximated.
[1] https://wiki.dolphin-emu.org/index.php?title=Ships_with_Debu...
I get that you're speaking relatively, but you and I have a very different idea of what qualifies as "a handful". Also, you could arguably add 154.02 million DS systems and 75 million 3DS systems if you include the slightly improved Super Mario 64 DS.
I'd consider the DS version to be its own game. I love it, but with such large changes to the core gameplay it's certainly not a port, and it's not a remaster. Personally I think Nintendo should just release widescreen versions of both to the Switch, maybe with Mario 64 DS being an overhaul DLC.
Porting the code is the easy part. The hard part is relicensing the original music, art, and other essential assets.
Consider the recent rereleases of Crazy Taxi, which were missing the iconic punk rock songs because a deal couldn’t be reached with the music companies. Not having the original music surely led to decreased sales. A THPS rerelease would probably face similar problems.
That build was made with either stolen source code or code decompiled and distributed without without a license from Nintendo. It is not comparable to an intentional source code release by the owner under some copyright license.
If it’s created by disassembling Nintendo’s code, then it is derived from that code and it infringes Nintendo’s copyright.
Anyway, I'm not saying that the Super Mario 64 decompiled code project isn't cool, because it is. It just probably infringes Nintendo's copyrights in the code, not just in the assets like levels, graphics, and music.
With so many remasters/remakes being released, it's obvious that studios care about their games, but I think it should be made obvious that releasing source is the real path to preservation. Look at the recent build of Super Mario 64 for the PC. The game went from being able to run on a handful of systems (13.56 million Wii U's, 101.63 million Wii's, 32.93 million N64's) to nearly every modern x86-based computer. And now that it's being ported to ARM systems as well, we'll probably see Mario 64 running natively on hardware for probably the next 25 years, well past the life expectancy of many of the systems it officially was built for.
Releasing source could also contribute to the bottom lines of the companies. By Activision releasing the source to Tony Hawk's Pro Skater 1-3 (please dear god I hope they do this), they could actually release those games on digital platforms like Steam or Epic using ports/code improvements they didn't have to write. Hell, if THPS1-3 were open sourced, I might attempt a port for the first time.