Is the Canon EF 180mm f/3.5L USM Macro Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 180mm f/3.5 test image. Observe the contrast and resolution of these results.
Is the Canon EF 180mm f/3.5L USM Macro Lens set to 180mm f/3.5 sharper than the Sigma 150mm f/2.8 EX DG APO HSM Macro Lens set to 150mm f/3.2? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.