Civilization series is great. You can build a mighty Empire, complete with roads, farms, railroads, etc. All depends on the strategies you have in mind. Can be compared to Total War series.
After reading the game info of The Sims Medieval, I came to know that you can build an entire kingdom. What I hope is to make a trading capital as I do in many other games. Build a huge marketing system, and then test my abilities in trading and warfare from what I have learnt in 7 years. Importing and exporting is fun, though.
What I do wonder is warfare. If possible, EA could implement thousands of soldiers on the battlefield (I highly doubt that there will be a
battlefield!). This game has knights, and knights were famous in Holy Roman Empire (known today as Germany), Poland, Austria, Teutonic Order (later, Prussia), Sicily, Napoli (today known as Naples) England, and most importantly, France.
Here is a group of French Knights, from the game Medieval II - Total War:
From the experience in Sims 3, I think that our computers will not be able to handle 10,000 soldiers on one 'lot' or battlefield. So the wars will probably be based on 1-on-1 duels between two kings/princes/wizards.