Civ II was pretty Civ-y, and had no stack combat - well, you could stack units indefinitely, but if that stack wasn't on a fort or city tile the whole thing would be destroyed if one of its units died to an attack. As such, stacks were actually dangerous for the stacker, which was pretty neat.
Fond memories.
Been a LONG time since I played Civ 2. I miss the animated advisors. "Let's go BOMB SOME HEADS, SIR!!!", "I disagree, sir!", "I disagree, sir!". Fond memories indeed. As for the (lack of) stack mechanics, they were painful since you had to move units one by one, and the risk of an entire "army" die because of a single unlucky battle against a lone unit was borderline retarded. One doesn't really have to wonder as to WHY they've changed it on Civ 3.
Stack combat became a thing with either Call to Power or Call to Power 2, evolving into the 'Armies' of Civ III and then turning into the late game borefest of Civ IV megastack combat.
Both CTP games had stack-on-stack combat with melee units on the front row and archers on the back. CTP brought fast combat resolution and was the ONLY Civ/CTP (they share the same root) game to actually take army composition into account when calculating battle results. Also, a warrior destroying a tank was 100% impossible on CTP, unlike Civ 3's "LOLRANDOM" combat system. Civ 3 and 4 never had "stack combat", but rather a heavily abstracted 1v1 until one stack was entirely destroyed. Both games had pretty similar combat, but IMO Civ 4 had less "lolwut??" battle results than Civ 3.
Not sure if this is a controversial opinion according to the bleeding edge of Codex thought, but Civ V definitely had better combat. It was its lack in other game systems that hurt it, in a relative sense. At least, until the BNW expansion.
Now, if only Civ V had the modding scene of Civ IV...
Civ V is
meant for brain-dead casuals, nothing more. Civ V doesn't have (and never will have) the modding scene of Civ IV because its core mechanics are utter shit. Wanna build stuff? FUCK YOU, HAVE SOME UPKEEP. Wanna expand your empire? FUCK YOU, HAVE SOME MORE UPKEEP AND ENJOY YOUR NEW SOCIAL POLICY COST, FAGGOT. Improvements? FUUUUUUUUCK YOOOOOOOOU.
I've never, EVER, hit the "end turn button" so many times and with so little hope on a Civ game. There's only so much fixing modders can do and modding the numerous idiotic design decisions out of that game is simply impossible. And the combat was also shit. Terrible balance, especially with civ-specific units, retarded AI sending its backline ahead of its frontline and MMOesque experience system. In fact, I remember a guy writting a guide to Civ V combat based on MMOs.
But, HEY, at least it had pretty animations and colors. If only modders could add an "awesome button"...
Also, this:
http://forums.civfanatics.com/showthread.php?t=381961
The reasons why this shitty game (along with whoever is responsible for it) deserves to die in a fire are well documented by the fine folks of the civfanatics forum.