i think every game that could theoretically run on an old computer or console should be ported to it
think about it, say you make a game for the game boy advance. not only can you play it on a GBA, but on any platform that can emulate or natively run GBA games (PC, mobile, DS, 3DS, gamecube, wii, wii u, etc)
the simpler the console, the more platforms could run the game. if you develop a game for the NES, you can play it on basically every console from the N64 onwards. if your game runs on a game boy, it can run on anything from a top of the line gaming PC to a 30 year old PC to a SNES
conversely, if you make a game that's really no more complex than an NES game but you develop it in unity or something, then you can probably only play it on a PC released in the last ~10 years
think about it, say you make a game for the game boy advance. not only can you play it on a GBA, but on any platform that can emulate or natively run GBA games (PC, mobile, DS, 3DS, gamecube, wii, wii u, etc)
the simpler the console, the more platforms could run the game. if you develop a game for the NES, you can play it on basically every console from the N64 onwards. if your game runs on a game boy, it can run on anything from a top of the line gaming PC to a 30 year old PC to a SNES
conversely, if you make a game that's really no more complex than an NES game but you develop it in unity or something, then you can probably only play it on a PC released in the last ~10 years