We started our game, and at first it went great. The only thing that bothered me though, was that while playing, the human player do their turn at the same time. And you won't believe me when I say this, but have you ever tried playing a turn based game with lag? Oh my word does it suck, at some stage our ping was in the double digits, and I mean seconds here (if only it was milliseconds!).
So, we played our game until about the late 1800's, but couldn't take it anymore, and stopped.
I was looking all over the internet for lag fixes and things like that, even doing my Borderlands 2 VPN trick didn't help much here. We have also always been looking for a play by email game, and I came across an awesome service called Giant Multiplayer Robot. Check out their website here: http://multiplayerrobot.com/
What these geniuses have done is create a little app and website that allows you to play Civilization 5 games by email. The big hassle about such games is the constant emailing of the savegames, but not with this little gem - once your game is set up, the small desktop app handles that for you, you just click submit turn, and it handles the uploading of your savegame to their server, and then notifies your friend that it's their turn to play.
We have now played about 100 turns like this, and it works beautifully! Check out their video below to see how their system works:
So, if you want to play Civilization 5 by email, then this is the solution you've waited for :) Enjoy!