Mike,
I understand where you're coming from; obviously the (very costly) additional stop available from the 200mm f/2 produces extreme subject isolation (bokeh) which, equally obviously, is what the 200mm f/2 lives for. However, just because you can shoot at f/2 doesn't mean you should. Depth of field at f/2 will be inappropriately (though impressively) narrow for some subjects at minimum focus distance. In addition, even though images shot wide open will be excellent, peak performance of the lens is likely to be around f/4. Moreover, the 200mm f/2 beats the 70-200mm f/2.8 @ 200mm in areas other than within the range f/2 to f/2.8.
For example, the Nikon 200mm f/2 beats the Nikon 70-200mm f/2.8 @ 200mm in resolution at comparable apertures down to f/8 inclusive. Therefore, when shooting at 200mm it is better to use the 200mm f/2 than the 70-200mm f/2.8. The Nikon 200mm f/2 also suffers less image degredation at comparable apertures than the Nikon 70-200mm f/2.8 @ 200mm when combined with teleconverters.
There is no reason to doubt that these findings would be similar for the equivalent Canon lenses.