They almost had it. Not sure what they were thinking.
Now the odd thing about this one is allegedly you are doing evil by making people happy. Lets just look at that statement for a second... I'm not entirely sure how the creative team and or upper management didn't see the flaw in that.
In the dungeon keeper series(not this game) you build a dungeon and dig in a similar way but the premise of that game is to make an overwhelming horde of monsters and destroy everyone in your path while protecting your own dungeon heart. In this game you build a dungeon to make heroes who enter it happy, when they are sufficiently happy then you can kill them ( you can kill them earlier but it defeats the purpose of the game). So essentially not only are you building a theme park you also have to chase down heroes to make sure they don't escape when they get sufficiently happy. It's a very odd not so good combination. Couple that with weak monsters even when fully upgraded as well as a weak signature unit and it's nothing but problems.
Conclusion : The game itself is a masked theme tycoon game with some silly plot and even sillier writing. (we took over areas by people knowing how awesome our dungeons are?) Requires a level of micro management of the "heroes" that just becomes tedious later on in the game. They tried to mimic what i think is a great game dungeon keeper but really fall short with some bad decisions on game play and plot.