Sharp C-41 is achievable. And it is not anything to do with how our eyes work, or 'perception of sharpness'. Line charts reveal that.

You need a sharper lens to reach the same levels I think with standard processing, or you can alter the processing.

Also your reproduction method and equipment matters a lot to anything decent off the film in terms of sharpness, flatbed scanners are very low res, they can be improved with 2-pass scan (separate files) and superresolution technique.

The following image I made should demonstrate a few of those points.

It is shot on Lucky 200, with modified C-41 developer.

http://oi43.tinypic.com/9glm6c.jpg