Here is the part of one of my posts in the Civ 2 forums dealing with Civ 4 (you can find the complete post also dealing with Civ 2-Civ 5 here:
http://forums.civfanatics.com/showpost.php?p=12123957&postcount=6):
Than came the "mega-catastrophe" called Civ 4. The Civ-world didn´t look any longer properly to me. Civ 4 (and later Civ 5) presents the world like a view on a toilet-brush. The units, buildings and cities on the map are standing all in different directions: What a mess!! This had nothing to do with the earth beeing round. It was a part of the high price of introducing a really not needed 3d engine to the game. The world is now presented in all three optical dimensions what in combination with the distortion of the proportion of units in my eyes leads to completely unacceptable results. The units now could be zoomed in again, but compared to Civ 3-units, they lost every second pixle, so they can be presented in the game. Civ 2 showed, that a good zoom function in a civ game is possible, even without a resource-eating 3d engine.
Another consequence of the resource-wasting 3d engine was, that this world now became much smaller to be playable than a world of Civ 3. The salesargument of Civ 4 for the restriction to now much smaller worlds was, that now the game focuses on the specialisation of cities. What a ...
As if it wouldn´t be common tactics since Civ 1 to cumulate the boni of improvements and resources in a city whenever possible. The number of civs in Civ 4 (vanilla) was also massively reduced from the 31 in C3C thanks to that completely unnecessairy 3d-engine. Even with these restrictions (at least for a long time) many civers had massive lag-problems with the performance of Civ 4 in the later phases of the game.
Of course the next feature that made Civ 2 "timeless" was also cut out in Civ 4. There was no longer an editor in Civ 4 and modding became extremely complicated compared to Civ 2 and Civ 3. I never forget, while assisting a good Civ 4 modder to do an interesting ship for Civ 4, the moment when it was noticed, that only the first of the many guns of that ship can fire (Edited: When looking in that thread, there was a time when not even one of the cannons of
HMS Warrior did fire). Modding became a privileg for an elite that needed more and more knowledge, the "modder from the street" focused in Civ 2 became an "outsider".
The combat system in Civ 4 on the first view seemed somewhat improved, but the best tactics with all these so-called "improvements" was to throw all units in a monsterstack, so all these so-called "improvements" in battle became very dubious in my eyes. The use of suicide-catapults against these monster-stacks had nothing to do any longer with history. They also could use flying burning pigs. Welcome in the world of comics! The idea of Sid to combine the features of a wargame (Empire) and the features of a construction game (Sim City) with history became severly corrupted. Civ 4 tried to make a cartoon out of the Civ series on a world like a toilet-brush and leaders like Mickey Mouse
!
With the Firaxian rule of thumb "one third new, one third improved, one third old" it was no wonder that nearly all parts I liked in Civ now in Civ 4 were cut out. So it´s no wonder I never liked Civ 4 and its expansions. But from time to time I try one of the Civ 4 mods to be somewhat informed about Civ 4. The worst thing is, that the ugly and resource-eating 3d-engine can´t be modded away. But there was still something good in Civ 4 - it had a handbook with a good analysis about Civ 3, that I used for my
Civ 3 epic mod CCM.
hence super spearman ..... 
