Just saw this detailed review and thought it would be good to post here. I agree with all of it pretty much.
Overall fun experience but with a lot of wasted potential and room for improvement. Ultimately not worth a replay. Nothing we don't already know. The expansion, on the other hand, was a big improvement in every way, especially story-wise. Obviously the devs understand their game better at this point and probably should have been how the base game was from the start.
Personally, I think most of this was fixed in Overlord II. Though, even that game has so much more potential!
We need more Overlord titles Codemasters!