Super Mario Bros. on the NES is considered a collector's item. This is because it is a classic and iconic video game that was released in 1985 and played a significant role in popularizing the video game industry. It was also a groundbreaking game that introduced many gameplay elements that are still used in video games today. As a result, it has a nostalgic value for many people who grew up playing it and a historical significance for video game enthusiasts. The game has not been produced for the NES since the 1990s, which means that copies of the game are becoming rarer and more valuable over time. All these factors contribute to the game's status as a highly sought-after collector's item.