I totally agree. On the other hand, discounting YA books is also a bit short sighted. Consider:

YA books are frequently the only way to get into a new genre. Every genre speaks in its own language, a language that must be learned through exposure. Books targetted at adults are often a poor way to learn that language because it makes assumptions about the reader. YA books are less likely to make those assumptions. Contrast Harry Potter with Lord of the Rings if you wish. (I have never even read the latter since it is inaccessible to me.)

It also short-changes YA books. I'm not going to claim that Harry Potter or Twilight are the heights of literature, but they are not the murky depths of it either. They are popular series precisely because they are well written. The Hunger Games is a great deal better than either if you take the time to look at what the author is saying. There are, of course, YA and childrens books that go far beyond those popular titles. For example: Awake and Dreaming by Kit Pearson.

I would also add the caution that many adult books are pure tripe, and some of them are even worse (they are pretentious tripe).