Simcity 4 isn't multiplayer. The best you could do is manage neighboring cities in a region, but only from the same game, not two different pc's simultaneously, I believe. Whether or not it's any fun is arguable. :laugh: It can range from great fun to annoyingly mircomanaging to frustrating depending on your patience and expectations, really. There are some mods to make it more enjoyable, but without multiplayer it's probably not what you're looking for anyway.
Agree with the COH comments, there's a lot going on at once. Not that I dislike that or can't do it, but sometimes I just want to blow stuff up and sometimes I just want to putter around and build things without frantically jumping back and forth. I always liked the Close Combat series in that regard - focus on the tactical aspect of the battle without having to manage any supply lines or bases.
How about any of the Age of Empires games, with an agreement that you don't start wailing on her until a point much later in the game?