Mesix
Obergruppenführer
To me, the difference between Emperor and Immortal is how you acquire the wonders. On Emperor you build the wonders you want. On Immortal, you build units and take the wonders you want.
if you want challenge, why not to play MP?
I'd also love to see two new difficulty levels. One between Emperor and Immortal as the OP suggests, and one between Immortal and Deity as some of the very experienced top players here suggest.
.. neilkaz ..
As I mentioned in another thread, I've come up with a way to make Emperor more difficult without relying on tactics that feel cheaty. (Trading tricks that only work because the AI has stupid amounts of money)
Basically, I immediately DoW every Civ on first contact and I never accept peace treaties. That forces me to be very careful about how I play, whether I'm going to be warlike or not, and it's a much closer simulation of MP, which is what I hate about Deity. Deity is harder in *all the wrong ways*.
Sadly, the only way I've found I really enjoy Civ5 Multiplayer is Hotseat though. Simultaneous turns = different game and ultimately less fun.
(Side note: Playing this way gives *really weird* results. The AI will offer insane deals for peace treaties at seemingly random times. It's awful tempting to take a deal when they offer 1000 gold and 3 luxuries, when I'm not even attacking them or near their borders)
There's an "Always War" toggle in the xml somewhere. Find it, switch it on, then it should appear in your advanced options menu and you can toggle it for future games.