First if you want to see the AI use better units and more of them play at Deity or Sid. You will see plenty of units and most will be better than yours for the first half of the game.
In order to deal with superior units you need to use superior tactics.
One of the ways is to use bombardment. I am not sure if that works for 10 times as you would have to have a lot of cats or what ever flavor of bombardment you had.
If you had better field positon and armies, you can get the job done.
The primary method I use to defeat stacks that are often 10 times mine is beachhead.
I drop a stack on a hill with a settler. I found the town on the next turn and rush a barracks or a wall. Fill any armies that may not have had all the units allowed, if any. Fort all units.
If I am lucky they cannot get to me on that turn and I can rush the wall or barracks, whichever I did not do last turn.
They send in the attackers and I cross my fingers. It is not uncommon to have 400 units hit me in one turn. I will have no bombardment units with me as a rule. I just prefer to bring as many troops as I have ships slots for instead.
Eventually I start to pick of wounded or stranglers and then go out on attack. I may or may not have gotten some bombardment units by that time.