Summary: I should have gotten this a while ago but enjoyed the base enough and there is plenty to do so I never picked it up. Spreading religion changes the game so much giving more play options as well as spies.
Summary: This is a sold DLC addon with a number of civs added, natural wonders, wonders to build, spies, and the religion system. However lack of a religion win dampens the going heavy into religion and if you are leading in tech spies are useless. It's a fun addition but not worth twenty-five dollars unless it's just spare cash.
Summary: I've been with Civilization from the beginning, and Civilization V adds (and subtracts) enough to keep me interested. Obviously, much of the game play is the same, and the Gods and Kings pack adds a few more layers of complexity. That said, Gods and Kings doesn't rock the world of Civilization, but fans of previous games will find it worth the money.
Summary: Admittedly, this is the 1st Civilization game I've played so I can't say how it stacks up against the others but it's certainly not the 1st game of it's type that I've ever played. I got it a while back while looking for XCom. It came in a 3-pack bundle with Civ IV (haven't played that one yet) and XCom (uninstalled this tripe after about a week) for ~$20.