As long as we are talking about old games that are still the gold standard, how is it possible no one has recreated the giant-god-monster and city management game Black and White yet?! That game was fantastic, and its premise so solid. It seems ripe for replication in more contemporary engines.
I never played Theme Hospital, but I spent so much time on the rest of those… Populous was so much fun. B&W was similar conceptually, but the kaiju aspect made it feel different. Slapping imps in Dungeon Keeper was fun all by itself, let alone the rest of the game. Fable was fine but I was more into other stuff at the time. I don’t think I played very far into it.