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.
Diablo 2 - I’ve played all classes, some in higher difficulties, again and again and it didn’t get old for a very long time. Today I’m not enjoying these kind of games anymore but I’m not sure why. Are they so different or has my taste changed so much?
I’ve quite recently made run of D2 up to middle of Act V and rhen lost interest at all. It was a bit grindy, but the main problem was convenience factor. I was at the point when my summoning Druid started to lack behind and it is pretty much impossible to respec skills to fight that sort of bad decisions… When I was a teenager I’d just scratch it and start over with better build, but ain’t nobody got time for that now!