Which installment of the Heroes series had the best campaign storyline for you?

The campaigns in Heroes of Might and Magic IV, especially the last three, are great. I like that, in addition to tactical and purely military themes, the plot also incorporates a love story (Elvin), philosophy (Gauldot), and rogueish intrigues (Tawn). Although Gauldot's campaign is something else entirely. When I played it, I didn't expect such depth of thought from a game that usually focuses mainly on politics.