Edit: holy gravedig Batman! This has to be a near-record.
AMG bruh!!! U Civ IV?!?
No but for real, Civ IV BTS is the s***. My all-time favorite Civ-style game. I still play LAN games with two friends almost once a month.
How long do you have to let the game run to hit 1,000,000,000 citizens though? I've never even gotten close to that. Although to be fair, most games I play don't get too far into the modern ages. We always start in the stone age and have progression set very slow, so even 6+ hours in you're maybe seeing gunpowder...