EASY way to make us fear the AI
currently the only way AIs can hurt my planets is by invading with transports, which are easily destroyed. in fact one only needed enough fast ships to intercept transports, and his planets are safe from any damage.
1 reason the MOO series AI seemed much more menacing was because they could declare war early, and hurt you badly without invasions. they could attack you before you even finished colonizing, and enter your orbits with ships. every turn they bombard, and you start to lose improvements and population
with galciv2 i have not seen AIs declare war before researching planetary invasion, which is an expensive and time consuming tech. even after planetary invasion is researched, a vastly underpowered player could still have no fear, because only transports can hurt him, and transports are very easily killed.
if galciv2 allowed planetary bombardment, a war declaration would make me panic, instead of just a "so what" reaction