It depends on what you mean by "general purpose computers", 8-bit computers like the Apple ][, Commodore 64 (and in Britain/Europe things like the ZX Spectrum)

It depends on what you mean by "general purpose computers", 8-bit computers like the Apple ][, Commodore 64 (and in Britain/Europe things like the ZX Spectrum) were actually quite popular before the NES. In fact many NES games were actually ports of earlier computer games.