Just finished my game on Emperor last night - and man it was a blast
I won in the early Industrial ages (after discovering Nationalism and Steam Power) by domination. I had 19 cities, while the 4 last remaining AI's had 1 each. The game took a total of 20 hours.
There are always some AIs who gets to build 2 cities, and man - they really grow strong if you don't snatch their spare city! At worst, I was about half an age behind 2 civs in my game!
When you get 4-6 cities under your control though, you have a chance to win the tech race. On Emperor, when I had 5 cities, I finally got to parity with the leaders - and soon I was half an age in front of everyone
What's very important in games like this, is military. You can't have enough units! I constantly see an AI from the other side of the map suddenly moving stacks of 30+ units towards my territory - and it's vital for me to get my units in place in time. Military will win you this game - as it's the only way of expanding!
The best tip for such a game is to build bombardment units - and LOTS of them! I used them for every attack (even on single Spearmen in the open) to redline the enemy - and after wiping out about 17 civs or so I had only lost 3-4 offensive units
It's very fun to play like this, as you need a whole different strategy than in 'normal' games.
I'll post a screen when I get home!
...and tonight I'll try it on Deity
PS: Someone asked if I've made techs cheaper - well I haven't, in fact I haven't changed anything except for max number of civs
