Best Castle Building/Defense game?

I recently decided to try out Stronghold 3. It seemed promising at start, but the campaign just felt too easy and unrewarding. And the game doesn't have a skirmish mode either (Facepalm), so i just stopped playing it.

However, i still feel that there is more to collect from this genre, however i have not found a single game so far that have what stronghold had in terms of creativity. The free placement of walls, that can also host troops. Towers, gatehouses, moats etc.

There are plenty of city-building games, but i am more interested in the war sector, and just building and building doesn't suit me. I find that on ordinary city-builders, you either succeed without problem, or crash completely.

Stronghold 3 had all of those things i had, except for free choice, due to it's lack of Skirmish. So now i am on the hunt for something similar, that allows me to do almost all of the things Stronghold let me. Most important is the free placement of buildings and walls that you can place troops upon with a big focus on creativity and player choice.

Economy shold be important, but the main focus should still be on defense and War.

I have been looking at the old Stronghold games, but their graphic just doesn't do it for me.

As i said, Stronghold 1 simply have too bad graphics. I'm usually not picky, but i'll set the limit on 20 pixels running around :P

The other ones you named arn't really castle builders, are they? I want to fight against a proper AI, not just waves of enemies tryign to get from point A to point B. Stronghold 3 had pretty much exactly what i wanted, except for the fact that it lacked skirmish mode.

I am going to strongly recommend the Dungeon Keeper series. You aren't building castles, but you are building dungeons. The object of the game is to build all the rooms and elements you need to have a successful dungeon, like a city builder of sorts. The difference is that you need to expand your dungeon into key areas, survive attacks, and eventually defeat enemy areas. It's not like a tower defense. The enemies are trying to attack you and destroy your dungeon, not just get from point A to point B.

Ok, so i tried Dungeon Keeper 2. It was fun at first, but it was simply too easy :/ A nice combination of RPG and Strategy though, but not exactly what i was looking for.