I'll add Minecraft to my previous post in this thread. I think it's had a massive impact on the gaming industry moving towards more player created content, and I don't think we would have the Super Mario Maker games, some of my favorite games ever, without it, but I always disliked its...
Pretty much any Metroidvania for me. I understand that people love the thrill of battling hard bosses and returning to previous areas with new unlocks, but it's a frustrating experience for me.
Old school Fire Emblem also falls into this category for me. Permadeath is a cool idea, but I...