Is the Canon EF 50mm f/2.5 Macro Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 50mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Canon EF 50mm f/2.5 Macro Lens set to 50mm f/4.0 sharper than the Sigma 50mm f/1.4 EX DG HSM Lens set to 50mm f/4.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.