Strangely enough, Celtic Kings has its own category here on JU. I did not know that.
Celtic Kings is a real-time-strategy game with roleplaying elements. Units gain levels, and there are hero units that lesser units can be attached to. The base building in this game is non-existant. You start with a full town, called a Stronghold, and cannot add any buildings to it. You also start with a village. There are two resources - gold, and food. Strongholds produce gold, while villages produce food. So, you have to ship the food back to the Stronghold.
Strongholds and villages are never destroyed, only captured. No buildings are destroyed in this game. Gates can be temporarily destroyed, but are easily repaired, though it does take a while.
That's what I really like about this game. It's not a 'build and destroy' game, but a 'capture the territory' game. Yeah, you still build units and fight, but you can play shadow-games too, and keep away from the opponent, but still harrass them by stealing their villages, outposts, and killing their transport mules.
Celtic Kings only has two races - Romans and Gauls. While this is limiting, it seems to work well in the simple context of the game. Gauls have lower cost, less big units, and Romans have higher cost, bigger units. As far as I know, there is no population cap, however only 50 units may be attached to a Hero.
The hero system also works very well. The hero keeps the troops in a formation. Without the hero, they will march willy-nilly everywhere, but with a hero everyone is in line. There are a couple different formations to choose from, such as line, block, and horse wings.
As far as the territory control goes, I think Rise of Nations has a better system. However, you can destroy all the non-city buildings in RoN, where you can't here. Therefore, you can take over and start building right away, as opposed to having to set up resource gatherers, and all that other micromanagement.
Celtic Kings really just takes the micromanagement out of the game. It tends to be broad-focused, where a single lost battle COULD decide the game, but doesn't HAVE to. More likely a building being taken or a successful blockade will turn the tides, and not a battle.
I really enjoy this game. It's simple, and it can play very fast or very long depending on the settings. There are two AIs to play against, too, defensive and chaotic, at each difficulty level, which are easy, medium, and hard.
I'm sure there's plenty more to say about this awesome game, but that's all I have for now.
It's fun!