If you're trying to pick just one game to play this week, you're going to have a bad time. For some reason it hasn't really felt like the fall gaming season to me yet. There have been little hints of it here and there, but overall it's all still felt more anticipatory than anything else. This week is the first where it's felt like faucet was truly open to full, and that the deluge had begun.
If you forced me to choose just one game this week, then I'd put my money down on X-Com. A modern remake by Firaxis of a PC Microprose classic.