-it's versatile. You can play it either in any browser, or on your iPhone. A great way to keep in touch with your Empire on the go.
-it's addictive. You'll always find yourself checking your build queue to make sure it's full and optimized.
-it's free. Following the popular microtransaction route, it's a free to play game, unless you want some boosts, to accelerate some actions, etc.
-it's created by a guy from Wisconsin. Can't go wrong with that.
-it's like SimCity in space.