Reddit user Lionbread has discovered that the PC version of XCOM: Enemy Unknown plays cinematics at 720p, but since the game ships with 1080p video renders included, players can switch to the higher-quality option with a little tinkering.
All it takes is attaching '1080_' to all the movie filed found in the 'Steam > Common > Xcom-Enemy-Unknown > XcomGame > Movies' folder. Take a look at the image below for an example.
In our XCOM: Enemy Unknown review we called the game a "turn-based masterpiece". It's definitely worth checking out.