Is the Canon EF 24-85mm f/3.5-4.5 USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 85mm f/4.5 test image. Observe the contrast and resolution of these results.
Is the Canon EF 24-85mm f/3.5-4.5 USM Lens set to 85mm f/4.5 sharper than the Tamron AF 28-75mm f/2.8 XR Di LD 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.