Cornell is a great show, but I think it's "legendary" status stems mostly from the fact that a really great sounding board was making trader rounds back when most shows being traded were still audience recorded....so it really stood out sonically. Now that there are entire runs available in great Betty Board quality, I'd say it barely makes the top 10 lists, if even, of die hards that collect and listen to every show they can get their hands on. In fact, it wasn't even the best show of 77. Maybe 3rd.
In fact, just about any show from May 77 is a gem, as are a few from March.
Same thing happens in the Zep boot worldwhere something in fantastic recording quality has gotten decades of repeated listens and the familiarity to give it "legendary" show status when there are many other shows from the same tour that are much much better. Even the film soundtrack The Song Remains The Same is a below average show overall for the tour. Baltimore from just a few nights before blows it away. But, my heart is still tied to those "legendary" nights at Madison Square Garden from having cranked it a thousand+ times. It does have my alltime fav Page solo from No Quarter though.