Wrath of God
A idea I had, maybe its already been done...
A brief cinematic displays the beautiful and prospering town, which is very well populated. Then, it gets to the fun part.
You enter the game as God. Then, by using uber overpowered triggers and spells, you control the city. For example, unleash a terrible plague that sends hordes of locusts to eat people, or meteor blasts to crush citizens. The town would auto-rebuild, oblivious to your destruction, fresh for you to terrorize again. Then, maybe the devil will visit and you SAVE the town for once.
Hmmm, what do you think?