I believe it has something to do with how the game seems to crop a majority off of the top of the screen, however the area at the bottom seems to always be visible by about the same amount.
That wouldn't cause the character's head to become aligned with a different part of the background.
Actually, it occurred to me that it's not the angle that's changed. It's the camera distance. If you compare the 4:3 shot with the widescreen, the PC is standing in the same spot in both shots, and the building in the distance is in the same spot, but the distance between them is bigger in the 4:3 shot. This suggests to me that in your widescreen shots, the camera distance is too far out. Or the 4:3 shot's camera distance is too far in. At the same time, widescreen makes the camera zoom in, which is not the opposite of increasing the camera distance - you can do both, and they don't cancel eachother out, but instead you get a weird depth distortion effect, which is why the distance between two landmarks which have not moved seems to have increased.