I am once again amazed by the level of stupidity some people exhibit every fucking time Civ IV combat is mentioned. What does all of this even have to do with Alpha Centauri? Listen here, retards.
The cost of units in "hammers" (or gold depending on civics/wonders) is constant. There is no "miniaturization" like in Moo2. So, essentially, you are throwing industrial production in form of units at your opponent. Spearman costs 35 hammers, tank 180, modern armor 240. Combat strength values are 4, 28, 40 respectively. Take in account that the way combat in Civ IV works, unit(strength) >> n * unit(strength/n). So strength 12 unit easily beats 3 strength 4 units, all other things being equal. There are also support costs for units to consider (lot of factors in play, but can be crippling for warmongering empires).
Now, would you rather have 1 modern armor or 7 spearmen? Or for that matter 1 MA or 20 spearmen? Only drawback to tanks/MA compared to spearmen is a resource requirement (oil, aluminium vs copper) and obviusly tech level needed. Mechanized infantry is a better all round unit, but as tanks can attack multiple times and have access to City Raider promotions, they are the best (ground) attacking unit.
Start BTS and try to kill a vanilla tank with a vanilla spearman, doesn't matter who attacks or defends. Go ahead, I'll wait. Post a video of your exploits. How many tries does it take? 1000, 10000? Or did you give up? Even if you stack all of defensive promotions on a spearman, put him in a fortress of a city and position a non-promoted tank in the worst possible manner, I think you can't get better than 20% odds vs the tank, even on defense. Now fire up Civ 3. Repeat the experiment. Apply Skyway logic. Conclusion: Civ 4 >> Civ 3.
As for spearman ever being able to "kill" a tank: shit happens, tanks break down; spearman represents a larger number of men wielding spears... There are a bunch of plausible explanations. Spearman unit is a hero and gets a huge amount of XP for the feat. I consider it a plus that the probability is not 0, but something like 0,00001. IMO, it adds not detracts from realism. As our BloodBowl players know, 97% chance is not a sure thing.
Now stop being a fucking retard and put this issue to rest, Skyway. Go play KOTOR or ARMA or whatever other garbage you like to play and stop parroting the same fallacious statements. Especially seeing as your pinnacle of Civ series has the "issue" much more pronounced. I really don't know what you get from this. Being negative I can understand, but repeating the same stupid shit over and over again...
Also, in before: scale of Civ maps/units is all screwed up
EDIT: I somehow missed this little gem:
Norfleet said:
Malakal said:
A tank has 28 base strength in civ 4, spearman has 4.
Yes, which means it only takes about 7 spearmen to kill a tank, and often considerably less.
Did you try to do this or are you just talking nonsense, like Skyway? Please, do try and report back. Keep in mind that losing more than 5 spearmen vs a tank means you're trowing hammers away (not to mention the support costs for a horde of spearmen).