Warcraft II: the units are not unique. For every human unit,
there is one equal and opposite orc unit with very similar
abilities. For example: Mage == Death Knight, Ogre == Knight,
Footman == Grunt, etc.
Starcraft: the units for each race are totally unique. For example,
the smallest Terran fighting unit was a Marine, which was very
different from the basic Zerg fighting unit (the Zergling).
