: Downloading ROMs for games you do not physically own is generally considered a copyright violation. Always use Archive.org responsibly and according to your local laws.
: The Internet Archive has historically operated under specific DMCA exemptions granted by the U.S. Library of Congress. These exemptions permit the circumvention of copy protection specifically for the preservation of obsolete video games and computer programs. All Nes Roms Archive.org
"NES ROMs collection on Archive.org — a community-contributed archive of NES/Famicom ROM images, scans, and metadata assembled for preservation and research; users should respect copyright laws." : Downloading ROMs for games you do not
On Archive.org, the "Nintendo Entertainment System (NES) ROMs" collection serves as one of the most comprehensive digital libraries for 8-bit gaming. It typically aggregates thousands of game files, ranging from official licensed cartridges to rare prototypes, unlicensed titles, and Japanese Famicom exclusives. Library of Congress
Titles from companies like Wisdom Tree or Tengen.
Once you master one game, you can consider the full archive.