I actually feel like Persia should be higher rated. They probably have one of the best UAs in the game: Not only do they get to enjoy the economic, production and cultural bonuses of a GA for 50% longer, they're also much more effective at combat. Their units cover more ground, they have better mobility for tactical maneuvers, and they're also respectably stronger in combat. Immortals are also a great UU; +10HP healed per turn is HUGE, especially if they have March, and the promotion stays upon upgrade as well. Persian Immortals or Pikemen or even Lancers in a GA can be quite deadly against any foe.
There's also the "Forever Golden" strategy to give an essentially limitless Golden Age if you build Chichen Itza, the Taj Mahal, take Representation and use Great Artists, all one after the other, providing a good way to clear what's left of the world late game. For more info see
http://forums.civfanatics.com/showthread.php?t=437142.
I forgot to mention Satrap's Court, while not the most powerful of the Uniques, it gives a bit of gold plus a nice happiness boost, meaning you can build this instead of a Colosseum or Zoo and benefit considerably more.