The Nintendo Entertainment System became so popular in the 1990’s that Nintendo Corp. had to campaign against calling all video game consoles a ‘nintendo’ in order to prevent their trademark from becoming generic. – WTF Fun Facts
Source: https://www.nintendolife.com/news/2022/04/random-heres-why-nintendo-doesnrt-want-you-using-the-word-nintendo-to-describe-video-games