Is the Canon EF 135mm f/2L USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 189mm f/3.2 test image. Observe the contrast and resolution of these results.
Is the Canon EF 135mm f/2L USM Lens set to 189mm f/3.2 sharper than the Nikon 135mm f/2D AF DC-Nikkor Lens set to 135mm f/2.2? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.