I had high hopes for Overlord. Having played older games such as Dungeon Keeper, I had different expectations than what Overlord turned out to be. Overlord takes a fairly novel concept (gather a horde of minions and take control of the countryside) and runs with it well, but a couple design issues keep it from being great.
My biggest complaint is a lack of variety in gameplay. Puzzles consist mostly of having the right type of minion on hand at any given time to break down a barrier, and manipulating your minions past traps to operate switches and other mechanisms. These puzzles, while interesting at first, quickly become repetitive. Combat breaks up the monotony, but the battle system is rather shallow, and besides controlling your minions alongside your character, is just hitting the attack button over and over.
Graphics and sound are good, and the characters' voice acting is a bit above average. Nothing stands out as exemplary, but none of it is annoying either.
Overlord is a good game, but lacks enough variety to really do justice to its premise. It's entertaining for a while, but doesn't do as much as it needs to keep players entertained for its full length.