Re: Dragon Age 2, Titan Quest and all things related
You could start with Rome. Very good game, the balance is nice, though the graphics are lacking in comparison to the newer games.
Empire sucked in my opinion, too many units and small percentages you have to look at to get a good army etc. Much too complex to have fun with.
Medieval II is pretty awesome, and I am still not sure what game is better, Medieval II or Shogun II. The AI is lacking a bit in both games, but Shogun offers alot of fun multiplayer stuff.
So I'd say, you can start with Rome, Medieval II or Shogun II. All three games are very good and fun to play.
P.S.: Sun Tzu > Machiavelli in my opinion ; )