Not every cartridge is a treasure, but some of the worst NES games are weirdly more memorable than the good ones. A mediocre platformer evaporates from memory. A broken game stays with you, because you spent an hour trying to work out whether it was you or the game, and it was the game. My shelf has a proud "infamy" section:

• Dr. Jekyll and Mr. Hyde, routinely ranked among the worst games ever. You walk right, everything hurts you, and your cane attack cannot hit most of it. There is a real mechanic buried in there, a stress meter that flips you into the Hyde side-scroller, but the game never explains it and the walking half is so hostile that almost nobody found out.
• Taboo: The Sixth Sense, barely a game at all. It's a tarot program on a cartridge: enter your name and birthday, it deals a spread and interprets it, and then it gives you lottery numbers. Rare developed it, which is the detail nobody believes.
• Silver Surfer, so sadistically hard it became a legend. Your hitbox is the entire surfboard, everything in the level including scenery kills you in one touch, and the Follin brothers wrote one of the best soundtracks on the console for it anyway.
• Deadly Towers and Hydlide, beloved punching bags of the retro community. Deadly Towers drops you into a maze with no map, enemies that respawn instantly and an item shop you can only reach by falling into the right hole.
• Bible Adventures, Wisdom Tree's unlicensed oddity where Noah hauls animals around. Wisdom Tree got around Nintendo's lockout chip with their own hardware workaround, which is why these carts are a different shape and why they exist at all.
• Bigfoot and Super Pitfall, ambitious, broken, unforgettable. Super Pitfall hides required items inside invisible blocks with no hint whatsoever.

I keep every one of them. A collection without its disasters isn't really telling the whole story, and honestly, the bad ones spark the best conversations.