As for Ulysses and LoTr, I like what my Amer lit 2 prof had to say. The definition of a 'classic' is something that we continue to read after an extended period of time.
It doesn't speak to an objective quality. Things that could have been classics may get lost in time, and things that were trash may become classics because there was nothing else big in the time period. If I compare the writing (unfairly, translations) of Beowulf to something written hundreds of years later, I may find the conventions of Beowulf archaic and wanting. Beowulf continues to be read (in my opinion) for historical reasons as much as for literary reasons. The work is old as dirt, and because people have found talking points for it, and it is in the mind of academics enough for us to continue finding talking points, why would we put it away?
For this same reason Harry Potter will not be a classic because academia is mixed on it. When people run out of stuff to say, it will only exist in its physical copies that may become less important once something else comes along (Say a story about young... mummies).
This is only partially related to objective judgment of writing, but I also think that you cannot objectively determine writing skill. As English changes, as our rules, likes, and style change, so will our objective view of things. Someone who writes in the block paragraph style of the late 1800s, isn't going to be as popular or 'good' now as they were in their own time. Now we like pop and fast movement, white space and dialog. This could change again, and then things written now would be seen as lesser, maybe we will call them 'sparse' and 'lacking'?