Keep in mind that roms are for back up if you OWN THE MACHINE! Emulators are the culprit allowing folks to play them, but even those are merely tools to confirm a valid copy of the ROM. Are they illegal? Yes. Should they be? Probably, but playing games that are otherwise not available anywhere on earth any longer are a good source of nostalgia and also help to promote the original author/developer’s work so it’s not exactly a lose lose here. Many younger folks would not even know what Mappy Mouse was or Packrat for example. I played those machines a Disneyworld back in 1985, and haven’t seen one but rarely in an arcade any longer, so do I play them when I see them. YES. Do I emulate illegally? I used to… not so much anymore since next-gen’s pipeline is chock full of new entertainment. But it’s still worth mentioning that at the end of the day, yes, they are illegal. Per Nintendo:
“There is a good deal of misinformation on the Internet regarding the backup/archival copy exception. It is not a “second copy” rule and is often mistakenly cited for the proposition that if you have one lawful copy of a copyrighted work, you are entitled to have a second copy of the copyrighted work even if that second copy is an infringing copy. The backup/archival copy exception is a very narrow limitation relating to a copy being made by the rightful owner of an authentic game to ensure he or she has one in the event of damage or destruction of the authentic. Therefore, whether you have an authentic game or not, or whether you have possession of a Nintendo ROM for a limited amount of time, i.e. 24 hours, it is illegal to download and play a Nintendo ROM from the Internet.”
As you can see they sate that it is illegal to download even with the original in hand.
Emulator/ROMS (Read Only Memory): Yes there illegal
Support the gaming industry by only buying and playing the games on the console they were made for.