If you like SimCity and Civilization you should try Settlers. I used to play it on PC. It's about building your medieval realm and conquer/beat your opponenet. It's different levels if I remember correctly. You have to balance resources and needs. It is a lot of micro management.
You can always play Reunion. It's available for AGA as well. It is a strategy game but it does follow a story line so you are limited what you can do. I remember exploring planets and wrote down on a piece of paper what kind of resources you can find where. It helped a lot when deciding where to build colonies. I did play this on PC as well but I want to try it on Amiga.