I think the computer cheats, and that is why you aren't economically superior to them.
-I've had capitols with 50 people in them, 6 people working each patch, and STILL could not beat the computers economically.
-I tried conquering another land (was playing on large islands - 3 gold, 3 iron, 2 stone), staffed the capitols and had 6 at each mine. Still no glory.
-Start a random game and have a computer start as an ally. Do nothing but watch your ally. In minutes an entire city is up and running, complete with military buildings. Where'd the wood come from?
-Also, you'll find that even if you have 6 improved granaries with 8 farms each, fully staffed, you'll find that the ally's 2 farms outproduced you (even though the AI seldom hunts on easy mode).