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.
Toe Jam & Earl. As a kid, it seemed just endlessly creative, you could just explore & explore forever. And the shit humor - I was the exact right age where every joke was a banger. Although the game itself would be badly dated today, I bet the music holds up well, albeit in short bursts. I still get snippets stuck in my head.