Now that I think about it, I second (or "third?") the thing about medium infantry or buffed up spearmen. I actually use lots of spearmen in my armies as main infantry (the ones with about 7att. and 14def. and bonus against cavalry) and that's fine in general. I agree knights should be limited.

Btw, a question/observation: should swords really beat spears? When I think about it, a sword is handled more swiftly so it could beat a spearman with agility, but the longer spear keeps the sword enemy at a distance. Of course this is seen from a one-on-one theory, and makes sense to me.
When I think of it as two units engaging each other, it'd look like a draw to me.