The Age of Kings is a vastly better game than the original, but the difficulty seemed to hold it back for me.
In The Age of Kings, there are four very different campaigns (5 if you count the tutorial), each has six missions, and you get to play as Joan of Arc, Saladin, Ghengis Khan, and Barbarossa. In each campaign you get to play as a different civilization, each with different strengths and weaknesses. And as it was with the original Age of Empires games before this, all the campaigns follow actual historical events, and they really teach you quite a bit about history during that time period. Also, there is as always plenty of things to build, from Barracks to a town market, and all that building is probably my favorite part of the game, very well done in that aspect.
The graphics for the game, I actually didn't mind even though it's a game coming from 1999, most of the characters are nice detailed, and for the main part the environments look pretty nice aswell. Through out the game I never really noticed the soundtrack, but RTS games aren't really known for their soundtracks, and it makes up for it any many other areas. The voiceovers are very well done, they match with all the characters very well. Still the main problem I had with Empires 2 was the difficulty, it's a pretty hard game when it comes to your enemies. Alot of times your enemies bases will seem almost impenetrable, probably the biggest culprit for this is the mission with Ghengis Khan when you invade China, The Great Wall never seemed so great!
The Age of Kings as I said before is a vastly better game than it's predecessor, and it added alot to the Age of Empires series, and can easily be recommended to anyone looking for a very nice, though difficult, RTS game.