People have posted Deity wins.
If you want to see what folks are complaining about with the AI there are a couple of paths. Choose an island map (another nice bonus: you get every ruins on the map, since the AI doesn't figure out that boats might just be a good idea.) Play Elizabeth.
Or play Alexander (quickest on Pangaia, doesn't really matter though). The only tech you care about are Horseback Riding and Bronze Working. The only building you need is a Barracks; two cities are enough. Build 4-5 Companion Cav, add in a couple of hoplites if you're feeling cautious, and just roll across the map. Puppet the capitals, raze the others, and if you want a better score grit your teeth and play on marathon.
If the AI played better at higher settings that would be one thing. But instead they just get a bunch of artificial advantages. I didn't like Immortal/Deity in Civ 4, even though I could beat them, because the AI was good enough that I had to "game the system" by taking advantage of AI quirks and game loopholes; I didn't feel that I was winning a normal game, because you couldn't win a normal game at those settings. Unlike in Civ 4, in Civ 5 they don't even play well enough with those advantages to even make it hard to win.
