I was amazed a couple of years back when I looked at a gallery exhibition of Ansel Adams' Museum Set. All were 16x20 from 8x10 negatives, I think. While they were wonderful prints, full of the virtuoso clarity of his technique and printing, they didn't look as sharp as I remember some of his other prints I've seen in the past. (My eyes are not as sharp as they used to be, either, so that may have played a role.) I may also have been spoiled by looking at the apparent resolution and digitally enhanced sharpness of inkjet prints.
Whether or not a big print from an 8x10" negative is needle-sharp is less important (to me at least) than the amazing overall quality of a print made from a big negative. It's an experience in itself. One of my strongest reactions to a print was to an Adams "Aspens" at his 80th birthday exhibition in San Francisco about 30 years ago. It was about 30x40", and it hit me right in the gut from clear across the room from the entrance to the show.