I'm going to get Steam and ONE game to play the next couple weeks. Never played computer games before. Just Xbox. So, what is your guys' favorite game if you had to choose just one?

I realize this will get generally downvoted, but I'm stuck in South Dakota for a week and want something to play. What game will keep me entertained? I've seen a lot from r/gaming about Portal and Mass Effect etc, but I'm clueless about all of it. Hoping to be sent in the right direction because you guys know your shit.