Well, no, since that comment is so poorly worded it's hard to tell what the writer was getting at, let alone whether it's correct. But what I took from it was that if only authors who achieved recognition in their lifetime were considered great, our body of "great literature" would actually be a body of shitty literature--presumably because, as I said, the commenter is one of those people who thinks that popular = shit, and that true greatness is only ever recognized after one is dead.

They're wrong. If only books that were popular in their day ever enjoyed the status of "classics" or "greats," we'd lose out on many books that deserved that status. But we'd still have, at a guess, about 2/3 of our current body of "canon" works.