Sides

Having sides that are different, and having more such sides, adds depth to a game.

Additionally depth can be added with a variety of units, such that the player can choose a build strategy (i.e. what units to produce) based on the particular scenario. For example, a map with lots of water will result in production of more naval units.

On top of this, each sides' units can having varying resource requirements, with different types of resources. Thus, a players strategy can be forced by the availability of resources. To achieve this, more types of resources are needed. This mechanism can also dictate a players strategy within a particular game, for example, choosing to conquer a particular area of the map to get access to a particular resource to allow production of a particular unit type (or set of unit types).