Campaign for Shades of Darkness: The Fall.

Generally, they are all cool, but I enjoy playing this one the most: XL.UNDERWORLD.8 PLAYERS (one of whom is me, and the other 7 are allies fighting against me), level 100 (medium, because the campaign is set to maximum, but resources are distributed equally).

Added after 15 minutes
In my opinion, "Heroes 3 forever."