Solo play definitely isn't as engaging. I tried all the Kingdoms campaigns once through. Not too impressed. The Americas campaign was the only one I didn't finish, not because of difficulty but because there are only so many mass infantry slogs I can bear.

Lately I've run up to the Mongols in BC 1.05 a few times just to get some decent battles. If I could trust the AI to manage cities and castles this would be a more viable way to run a SP campaign. I couldn't get started on the 3rd Age mod.

Haven't bought Empires. Lots of bugs left to shake out before it looks playable to me; I am not a beta tester.