I'd say my favorite race is Protoss, but jokes aside, I love the Bablyonians. A civilization that's all about being greedy for science, they not only fend off early aggression like a breeze with their exclusive Walls of Babylon but also are rewarded for being incredibly greedy with early research choices as well. Whenever I play a multiplayer match as them, my friends always get mad when I bring up the fact that they are still are incapable of making more science per turn than me, just like it was in the Ancient era, and the Medieval era, and so on. It's really funny and I always find a special satisfaction in exploiting my technological superiority. My second favorite civilization would have to be the Germans. When your on a continent with someone else that isn't militaristic and there are a lot of barbarian encampments, you can create an army and take cities almost effortlessly.
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Nosce te ipsum - Know thyself