Battlestar Galactica

The reimagined Battlestar Galactica series is one of the finest examples of space opera out there.  The human race is cast out from its colonies by it's own creation, the robotic Cylons, after a sneak attack during a time of truce results in nuclear devastation of all of their worlds.  Start off with the mini-series that started it all, then watch all seasons and the made for TV movie Razor on Netflix.