It's not winnable, though. One side can project force at interstellar distances, the other side can not.
There can be no "killing" the alien, as they can retaliate with weapons that can destroy our only world and we can not locate much less reach even one of theirs.
Analyzing with game theory only works if you can correctly model the environment you are studying. It is one of the best tools in our arsenal, but you need to know how to use it. In the case of interstellar contact, the case for hostility is thin.
As observed by others here, there is nothing to gain from conquest that can not more easily be gained in the vastness of uninhabited space. Once you are sufficiently advanced to traverse the stars, and can muster enough energy to do so in force, you can easily obtain the all resources you might want locally and without contest.
The only thing that can be gained through initiating contact, are those things you can gain through cultural exchange and trade. Namely, diversifying your own knowledge base and scientific methods by injecting ideas that your own culture did not invent. This happened numerous times locally on our own planet, and the effects have led to such things as the Renaissance.
That said, I look forward to playing this game as mercilessly as possible.