I would recommend the Age of Empires II game first. That was one of the first games in this genres I played in this genre (real-time strategy), and I played it a lot in my childhood.
Another similar genre is the turn-based strategy.
I would recommend the Heroes of Might and Magic video game series from this genre. Especially the Heroes of Might and Magic 1-2-3. Many people like this video game series. Especially the third episode. My favourite is the second episode. I played that game a lot in my childhood, and even as an adult too.