I'm afraid, it's a feature of the Battlefield 2 engine - in display modes wider than 4:3 it chooses the middle between increasing the field of view and stretching the picture. In my experience, you will stop noticing that after some time.
The "Aspect Ratio" option in the launcher only affects the HUD by adapting it to the aspect ratio, it can't fix the "fat" objects and ovals in 16:9, sadly.