There's actually a pretty wide distribution of video game installation sizes. People are responding to you with the stats of some of the largest games out there, but they aren't normal games. They're AAA open world and FPS games, which are all the way at one end of the distribution. Some new games I've played in the last year are right around 1-2 gigabytes. If I downloaded another Civ-style game, and it was 20 gigabytes, I'd be surprised... but not outraged or shocked.