An emulator of a patent-expired console doesn't infringe.
Which narrows the question: If the NES patent
hadn't expired, such as in the case of a
Cher Patent Act, would an emulator infringe? Does a PlayStation emulator infringe? My guess is no because
Sony lost to Connectix and Bleem in court, despite winning the war by bankrupting both companies with attorney's fees, forcing Bleem to close and Connectix to sell its assets to Microsoft and Sony.