The original immersive god game?
You controlled a small island with a small population and had to compete against another god, with his own population, as you made life better for your little folks, your mana grew...and this is where the fun really manifested itself.
As you gained mana, and thus power, you could cause earthquakes, volcanoes or floods...anything which would either improve life for your bods...or wipe the opposition's out.
This game sparked a number of copies over the years, and is probably responsible for the highly popular god sim genre.