I've done a similar project before (taking an NES game I like, disassembling it, and doing a PC port). For me, the attraction is being able to make an ideal version of a game I like, with bugfixes, quality of life improvements, added polish, and not having to deal with hardware restrictions from old consoles. The amount of effort involved doesn't really make sense unless it's something you deeply care about, which is why most commercial rereleases of old games are emulated instead of this sort of improved native port.