Interesting the criteria are specified to "Light Novel" and not including webnovels.
That said, if we were to stick very strictly to only Light Novels, I'd definitely list Ascendance of a Bookworm as quite likely the best LN ever written.
If we were to expand the criteria to include Webnovels, I'd also add Mother of Learning and Worm.
That said, listing those off just made me realize. The west has a SERIOUS problem with it's WN to published novel pipeline. Both of those ones I just listed are incredibly well written and also incredibly popular to the point where it's absolutely baffling neither one of them has been picked up by a major publishing house.