Is the Nikon 24-70mm f/2.8G AF-S Nikkor Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 28mm f/8.0 test image. Observe the contrast and resolution of these results.
Is the Nikon 24-70mm f/2.8G AF-S Nikkor Lens set to 28mm f/8.0 sharper than the Nikon 14-24mm f/2.8G AF-S Nikkor Lens set to 14mm f/3.2? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.