Hegemon Gold: Wars of Ancient Greece is excellent with the follow up, Rome due later this year.
http://www.longbowgames.com/hegemony/history/
http://www.longbowgames.com/hegemony/history/
Why not download it on Steam the F2P part try it out and then see if it is worth getting the DLC that's what I am currently doing. Although I am not convinced it is worth it to be honest at this present time.
Here comes a silly question. I bought the game on Steam, the £9.99 deal, but it's not showing up in my games library. Where do I download the client?
Forgot about the dune games, try Empire: battle for dune.
At the moment I'm playing Wargame and Shogun 2, both of which are very good RTS's.