The Neo Geo (Japanese: ネオジオ Hepburn: Neojio), stylised as NEO・GEO, also written as NEOGEO, is a cartridge-based arcade system board and fourth-generation home video game console released on April 26, 1990, by Japanese game company SNK Corporation. It was the first system in SNK’s Neo Geo family. The Neo Geo was marketed as 24-bit; its CPU is technically a 16/32-bit 68000-based system with an 8/16-bit Z80 coprocessor, while its GPU chipset has a 24-bit graphics data bus.
You can browse and download most available games for free below, but you will need an emulator also to play them. For Neo Geo we recommend http://www.neoragex.fr/ but you can use any emulator of your choice and even original hardware if you have the know how!