Freeciv is a Free and Open Source empire-building strategy game inspired by the history of human civilization. The game commences in prehistory and your mission is to lead your tribe from the stone age to the space age. Please note: Versions of Freeciv provided here may not be the most recent. To acquire the most recent version of the game, please visit the project at their website.
I give this a 10 since it is very playable, has lots of units/nations/development strategies and almost limitless variations in the game play. It is also free and one of the (few) games on Android without commercials. Even if it plays/controls slightly better on a PC, the Android version is still ok.
fun game