The Age of Empires, Age of Kings, Age of Mythology series is definitely the best ever sires of real time strategy games.  In all versions of the game you are allowed to control both the armies and economies of your nation.  You can build buildings, creature soldiers or peasants, even priests.  Your peasants you command to do the different menial tasks such as farming, mining, and building castles.  While your armies roam the land either defending your peasants, sieging enemy castles, or raiding their peasants.  Priest have the power to convert both peasants and soldiers.  If you like being king of the world, this is for you.  Finally, I just want to differentiate between the games.  Age of Empires is the oldest of the games and should run on any computer, but I wouldn't recommend the game without either the Rise of Rome Expansion Pack or just buying the Age of Empires Gold Edition.  These two correct many problems with the original Age of Empires.  Next game up the latter for medium computers is Age of Kings (that's what I'm still playing.) It can run on just about any computer with sixty four megs of ram and a two hundred megahertz processor.  I use it on a five hundred megahertz and a one point four gigahertz.  Next game up is the Age of Mythology.  This introduces a whole new realm of playing to the sires.  This one you civilization chooses different gods to worship and is given power from them.  Unfortunately you only get two really spectacular god powers each game and you can only use them once, but then it keeps the game to more strategy and less luck and wildcards.  (It is fun to get the wildcards when you have them though!)  This game should have a processor of I would say at least a six hundred and a graphics card at least thirty two megabytes; and lastly this is not the game for everybody.  I still use Age of Kings/Conquerors not because of my computer, but because I don't like all the crazy stuff in Mythology; I think it distracts from the medieval battle tactics.  Really choosing between Mythology and Age of Kings is just a matter of personal opinion.  I'd say download both demos and try them both; or if you have the money to blow, buy them both.  Either way I think you'll love both of them.  Well that's all for me.  This is just a general over view don't take my words as gold check out the specs and requirements yourself.  I just wanted to help point you in the right direction.