And Why the Industry Misses the Point
I am going to take a somewhat unpopular stance: I really like stereoscopic 3D. I also expect to change your mind and get you excited about stereoscopic 3D too - unless of course a circumstance such as monovision interferes with your ability to see 3D at all. I expect to accomplish where the industry has failed simply because I will not ignore the benefits of 3D in my explanation.
Firstly - we see a crisp image when our brain is more clearly able to make out objects in a scene.
We typically have two major methods of increasing the crispness of an image: we either increase the resolution or we increase the contrast of the picture. As resolution increases we receive a finer grid of positional information to place and contain the objects in the scene. As contrast increases we receive a wider difference between the brightest points and the darkest points from a scene which prevents objects from blending together in a mess of grey.
We are also able to experience depth information by comparing the parallax effect across both of our eyes. We are able to encapsulate each object into a 3D volume and position each capsule a more defined distance apart. Encapsulated objects appear crisper because we can more clearly see them as sharply defined independent objects.
Be careful with this stereoscopic 3D image. To see the 3D effect you must slowly cross your eyes until the two images align in the center. This should only be attempted by adults with fully developed eyes and without prior medical conditions. Also, sit a comfortable distance away so you do not need to cross your eyes too far inward and rest your eyes until they no longer feel strained. In short - do not pull an eye muscle or something. Use common sense. Also move your mouse cursor far away from the image as it will break your focusing lock and click on the image to make it full sized.
Again, be careful when crossing your eyes to see stereoscopic 3D and relax them when you are done.
The above image is a scene from Unreal Tournament 3 laid out in a cross-eyed 3D format. If you are safely able to experience the 3D image then I would like you to pay careful attention to how crisp the 3D image appeared. Compare this level of crispness to either the left or right eye image by itself.
Which has the crisper picture quality?
That is basically why 3D is awesome: it makes your picture quality appear substantially better by giving your brain more information about the object. This effect can also play with how the brain perceives the world you present it: similar to how HDR tonal mapping plays with exposure ranges we cannot see and infrared photography plays with colors we cannot see to modify the photograph - which we can see - for surreal effects.