First, only input resolutions that your video card are capable of. Second, make sure your monitor or capable of using that resolution as well.
How about you tell us the model of your Monitor and Video Card.
Try to find out what the recommended resolution for your monitor is and use that.
Bring up the map in the game and see if your radar circles are actually circles, or if they are stretched.
Just to let you know, since you want a widescreen resolution, you will not see more than 90 degrees field of view. Instead, the game will crop or cut out some portion of the top and bottom.
In the end, widescreen means you see less for this game.