And most of them are ... unless it is in a crescent phase.
We can learn something here, though. When viewing Saturn, Jupiter, Mars and all the other 'outer' planets, we always see them as round objects - spheres in space. One face is always illuminated by the sun because they are further from the sun than we are. The Earth is between the sun and those planets, so we always see them as fully illuminated.
In the case of Mercury and Venus, though, those planets are between the Earth and the sun. Because of that, they can move between us and the sun. When that happens, we see them in phases - just as we seen the moon. If Venus is exactly opposite the sun from Earth, we see it fully illuminated as a sphere in the sky. If Venus is directly between us and the sun, we can't see it at all, because we are only seeing it's 'dark side.' If Venus is at a 90-degree angle from our direct path to the sun, we see it as a crescent.
Today, Venus is nearly fully illuminated. Because it is so bright, it's difficult to resolve the sphere at such a low resolution, so you basically get this unremarkable photo. :)
Image courtesy: http://www.skymarvels.com/infopages/vids/Venus%20-%20Current%20001.htm