I'd like to recommend Lands to Conquer. It's a fantastic mod for A.I and diplomacy that does an extremely good job of making the opponents behave more realistically.

As a bonus it also does a great job of keeping the overall feel of the game the same, although it changes more than VanillaMod

Using Lands to Conquer you certianly don't seem to get backstabbed as much, and friends tend to stay friends for much longer. It's also a more challenging, balanced game.

It was made by Lusted, and so good that CA hired him!