I agree that I haven't seen a great deal of use for catapults. However, if you have a game that lasts into modern times, invest in artillery pieces. You won't regret it. 
I had a combined force of Persians and Russians stage a massive land invasion at one point (with the Americans doing the same on another front). Said invasion force included a Persian army unit of cavalry.
Cities in the front line point artillery pieces at the Persian army unit. Four bombardment attacks per turn. The army unit quickly retreats.
I had a combined force of Persians and Russians stage a massive land invasion at one point (with the Americans doing the same on another front). Said invasion force included a Persian army unit of cavalry.
Cities in the front line point artillery pieces at the Persian army unit. Four bombardment attacks per turn. The army unit quickly retreats.
