Why is Civ IV the favorite of hardcore players?

[King Lewie XIV]

I'm aware from what I have read that IV is the favorite of the Series for hardcore players. I just wanted to know specifically why? For me, one big thing is I love how big and powerful the cities can get in IV. It just doesn't feel the same in V nor VI in this vein. Also, the Great People are more fun in IV. You can keep stackign them in a city to get some huge bonuses. I think VI is too much about getting the right adjacency bonuses. Also, I am fine with the military of IV, I don't crave extra military strategy, I'm ALL about building a grand civilization. Anyway I would love to hear what you guys think.