I am not sure what I have here for consoles of that vintage. Got plenty for later stuff and PC but consoles is a harder ask. Most of what I would look at is instead sorting little niggles, censorship, minor bugs that most would not encounter, stuff that dragged it down only a little bit (see something like Mario 6 golden coins fixes) or more of the same level expansions and whatnot.
There were a few attempts to improve the castlevanias.
While I highly recommend looking up the fixes for that game, and the explanations of things that people made to go along with it, was it that bad to begin with?
I forgot to mention Final Fantasy VII on NES.
Sonic the Hedgehog on NES. Also Super mario World on NES.
Do homebrew/years later bootleg fan games count here?