Here's the why so you know what you SHOULD set it to.
FOV = Field of View.
Console ports almost always get this wrong for PC. Generally, human eyes can see a 180 degree field of view. However, in dealing with computers your "eyes to the world" are limited by your monitor/TV and it should be set to something that makes visual sense to your brain. Here's the thing... On a console, sitting on your couch 10 feet away, your field of view to your TV is around 40-60 degrees. And that's generally what the FOV is set at for console games. On PC, however, you're sitting at your computer station inches from your monitor. If you were to take a compass and measure the angle of the viewable space (can even make an L or V shape with your hands to approximate), you'll come out to around a 90 degree field of view. So a PC game should be FOV 90...85.. somewhere around there. Devs like DICE (Battlefield 3) appreciate this console vs. PC difference and make the FOV readily adjustable in the in-game options for PC. The other reason for getting it right is some folks are sensitive to abnormally low FOV and can become nauseous if the field of view is much smaller than it should be.
In an ideal world, a game would load up, know the size of your monitor, the distance it is from your face and set it's FOV perfectly to match.

Example:
Random game FOV 62 degrees: http://i.imgur.com/w8H3e.jpg
Random game FOV 90 degrees: http://i.imgur.com/ZG9pe.jpg