Not a crime as such, but how does one dump a ROM without making copy, and how does one get the right to make copies if Nintendo won't license you the content? It's fine to make an policy argument about the the law aught to be, but you can't just ignore what it is.
The reason making a single copy for personal use is generally considered permissible is because: (1) it may be fair use under 17 USC 107, (2) the copyright owner will probably never find out, and (3) even if the copyright owner found out it probably won’t sue over one copy.
https://www.gov.uk/government/news/quashing-of-private-copyi...
Personal copies are legal... Just like I can take a patent, build the thing and use it myself, I just can not make commercial product and sell it.
This is why I am not aware of anyone ever being sue or otherwise held to account for DOWNLOADING copyrighted works. They always Sue over DISTRIBUTION. BitTorrent got the tag of "Sued for downloading" but in reality people were sued for seeding, ie distributing. I am not aware of any leecher that was sued.
Similar of Usenet, Uploaders, and usenet providers get sued, but downloaders?
The entire point of copyright is about preventing unauthorized distribution,
So you must have missed all the filesharing lawsuits over the last 25 years. Lots of people got sued for just downloading, not seeding, just downloading.
Copyright is primarily about copying.
https://www.law.cornell.edu/uscode/text/17/106
Subject to sections 107 through 122, the owner of copyright under this title has the exclusive rights to do and to authorize any of the following: (1) to reproduce the copyrighted work in copies or phonorecords;