User blog comment:ShermanTheMythran/Civilization V - Free Weekend!/@comment-4257955-20130607002425/@comment-4052371-20130607022345

Civ IV is much better than Civ III. Civ III is extremely unbalanced. A spearman unit can destroy a modern tank unit in some situations, which is plain ridiculous. I've seriously lost a city before, because a bunch of mounted units destroyed my tanks.

And plus, Civ IV has much better graphics, much better modding support, and unit promotions where you can specialize units to fight against certain unit types or in specific types of terrain (which is much better than the old Civ II system were the unit gained a health point). And the whole mechanic where a city completely shuts down because the citizens want entertainment is stupid. IDK about Civ V though.