Which faction do you like the most?

Dark Elves are the most original race in the game... And the others have been stuck in their own rut for years with almost no changes!

I agree with this. In Heroes 3, it's Dungeon; in Heroes 4, it's Chaos (in Heroes 4, I liked both Academy and Chaos, but since I always played as Academy in Heroes 3, I also played as it in Heroes 4); and in Heroes 5, I completely switched to Dungeon.
This race is completely different in each part of the game (unlike... everyone else).