I think it is underappreciated just how much additional sharpness and detail a high resolution sensor can produce from any lens whatever its quality.
Part of the reason for this underappreciation is due to the fact that most manufacturers tend to dribble out small increases in sensor pixel count so there's no significant increase in resolution, due to the sensor, that's obvious.
For example, within the Canon APS-C range, I progressed from 6mp to 8mp to 10mp to 15mp. The next upgrade, the 18mp 7D, is a mere 3mp more, which I didn't buy because Nikon seemed to be offering a level of performance which I preferred.
The biggest jump in pixel count in the Canon models is between the 10mp of the 40D and the 15mp of the 50D. Having taken the trouble to compare resolution, visually, using a good prime, such as the Canon 50/1.4, I found that the 50D produces sharper and more detailed images at all F/stops (except F22) to an extent which is so obvious that, were I testing different lenses in a shop before buying, using the 50D, and I saw such differences, there would be no doubt at all which lens I would prefer.
In fact, I'm asking myself the question if any prime lens exists, at any price, which could match, when used on the 10mp 40D, the level of detail possible with an average zoom used at the same focal length on the 15mp 50D, using each lens at its sharpest aperture of course.
I doubt such a lens exists.