Still, have you noticed 3D games don't suffer as much either??
Indeed I have. I think it might have something to do with the way that, in 3d games, you're mostly focussing on the centre of the screen (the point you're moving towards) as you move... and that part of the screen is actually moving quite slowly. In a 2d game, everything is scrolling at the same rate, and the image is static, so the smearing becomes really obvious.