The first game that comes to mind for me is Civilizations 4. I’ve probably spent hundreds of hours playing but after getting used to 5 and 6 I have a really hard time going back. Going back and forth between 5 and 6 I need to rethink some strategies but with 4 I feel like I need to rethink everything. I don’t know if it’s because of the tech tree layout in combination with the civics system, things like unit stacking, or maybe just a bunch of little things but it takes me a while to readjust.
7th Saga. It’s a turn based top down RPG (similar to Final Fantasy 1 or Dragon Warrior 1). The games AI sometimes just kills you (and takes great delight in it). Easily the most frustrating RPG I’ve played.
Blaster Master for the Nintendo (NES) as well. Instead of evil AI you get evil level design that wants to kill you.
Now if you’ll excuse me, I’m off to have a sandwich and play some Leisure Suit Larry 3.