StarCraft has one of the most accurate science fiction technology and their lore. For example, the Marine unveils to things: the best Military branch of the United States and the United Kingdom, with an appearance resembling astronauts sent to outer space. The StarCraft II version of the Marine, and including the development of constructing a Marine reveals to show how realistically the armor can be built along with a given survival capabilities within the suits. Another example would be the biology and evolution of how the Zerg strain works, even a newborn one second old Zergling is much tougher than a vicious adult twenty year old lion.
With the storyline, the first campaign rising the Sons of Korhal to overthrow the Terran Confederacy along with betrayal and given propaganda. Very deep and military strategic. The second campaign resembling of the Zerg forces to overthrow the Protoss in their very homeworld. And the third campaign actually have a civil war then uniting and alongside with Raynor's Raiders to defeat the vile Overmind. The fourth campaign revealing the survivability of the Protoss, especially on planet Shakuras, the planet of the Dark Templar. And now, the fifth campaign, the small fleet expeditionary force of the United Earth Directorate completely overthrows the Terran Dominion with an iron fist along by defeating the second Overmind by only using an Engineering Bay and a few dropships full of medics to tame the Overmind. Despite the betrayal of the double agent Samir Duran, the UED manages through. Lastly with the sixth and final campaign, revealing an alliance between Kerrigan's Zerg, Terran Dominion, Raynor's Raiders and the remaining survivors of the Protoss covertly defeating the small fleet expeditionary force of the United Earth Directorate. But in time, Kerrigan's betrayal completely divided the pact and definitely weaken the expeditionary UED forces.
In summarizing, basically:
Sons of Korhal + Absorbing Confederates (Raynor, Magistrate, Duke and Kerrigan) > Terran Confederacy
Zerg > Protoss
Protoss + Raynor + Dark Templar > Zerg
Protoss > Renegade Zerg (following Protoss refugees)
Small United Earth Directorate Fleet > Renegade Zerg + Protoss + Terran Dominion
The Kel-Morian Combine < Raynor + Infested Kerrigan + Protoss + Remnants of Terran Dominion > Small UED Fleet + Zerg Slaves
Hopefully in StarCraft II:
Raynor's Raiders + Umojan Protectorate + Remnants of the UED > Terran Dominion
Kerrigan's Zerg > Raynor's Raiders
Xel'Naga < Protoss + Raynor's Raiders + Umojan Protectorate + Remnants of the UED > Kerrigan's Zerg
Protoss > Xel'Naga
Xel'Naga < Third Overmind > Protoss + Raynor's Raiders + Umojan Protectorate + Remnants of the UED + Uninfested Kerrigan
Second Fleet of the United Earth Directorate » All
None.