Here are a couple of resources for finding human opponents:
This is a very cool looking site that manages games. The only problem is that it won't work with 1.35. The new patch should correct that.
http://seiv.admiral.com/index.html
There is a PBEM interest group on Yahoo
http://Groups.yahoo.com/group/SE4-PBEM
I think you will find playing humans much more interesting than the AI. For example, humans won't surrender to you--they surrender to their ally or your enemy or do whatever they can to make things hard for you.