Today I'm going to suggest the game Reus. This is a world simulator much in the style of say Populous or Black and White, but the scale is (despite including the entire world) limited. I would say that Reus, at least at the early levels of play, is more of a puzzle game.
You control 4 giants who each have elemental powers. These giants can terraform sections of the planet to make them habitable and create resources for civilizations to harvest. The Civilizations then start a project which require certain combinations of resources. Completing these projects adds new abilities to your giants allowing them to create more varied resources. Resources have synergies that need to be exploited to get the most out of them. If you plant two Blueberries next to each other and then upgrade one to Strawberries it creates synergy, but if you upgrade both patches to Strawberries then that synergy fades. Each plant is high quality but is getting no bonus and is less valuable.
The game is played in pause-able real time. The giants move across your world very slowly and the civilizations take time to react to the resources you create for them. While it is possible to play the game in a really focused and deliberate way, using pause to make sure that all 4 of your giants are always doing something, it's also possible to just sit back and casually watch your giants toddle along making mountains and oceans and watching your cities grow. I think to play at the top tiers some focused and deliberate play is probably needed, but I've only just gotten into the 60 minute era.
Play time is, I think, this games greatest feature. You start out with the ability to play a 30 minute "era" and there are a list of achievements, goals, or unlocks to shoot for. Once you've performed a certain number of these tasks the 60 minute era will unlock with a whole new set of goals. Eventually you'll open up the 120 minute era with the final set of achievements. It looks like there is also a set of challenge modes at the bottom of the list. My biggest problem with world building games is the infinite time sink that can go into a single game, and while that is a possibility with Reus it is not the core design. This game is built to be a time challenge and I think it works at a casual and hard core level.
So far I have played for about 7 hours and I've hit a quarter of the goals in the 2nd era. I also am still learning a lot about how to maximize productions to create tier 3 and above projects.
Reus has a list price of $10, and is currently 25% off as part of the Steam summer sale. So go, pick this up. Have your Mountain Giant create a bunch of advanced minerals and your Swamp Giant create loads of herbs. Cover your planet in scientific wonders and call it Nexus.
Mike B did an Indie for Breakfast on this title at the beginning of the month, you can watch that if you'd like to see a 30 minute era play session in action.