Archive.org’s NES ROM collection is a paradox. It is simultaneously one of the most important digital preservation projects of the 21st century and a blatant, if morally defensible, violation of copyright law.
For many retro gaming enthusiasts, the Internet Archive is more than a website; it is an "on-demand" museum. It hosts massive collections of NES ROMs, ranging from complete licensed libraries to rare prototypes and fan translations. archive.org nes roms
If you decide to explore, here is the responsible path: Archive