Dungeon Keeper 1 is still one of my favorites.
I have played 1 and 2 lots.
Multiplayer runs much faster on the second game though, for players that play with higher latency for online play.
There is a remake also that is very active @
http://warfortheoverworld.com.
Also a already playable fan expansion @
http://keeper.lubie.org/html/dk_keeperfx.php, but the multiplayer is very buggy at the moment with more than 2 players, and it can be played online by TCP/IP, and works well on Windows 7 when I tested.
One very odd thing about the Dungeon Keeper 2 engine which I don't think I liked much was that it's unbalanced fighting. If you attack from the south side all the time, you will always have the advantage in defeating your opponents, even with the same type of creatures vs. the others.