Thanks for the question!

In answer to your first question, I think questions could easily be as valuable! This aspect of Steem hasn't really been explored yet, but it's one of the original goals outlined in the whitepaper. If essays on Steemit are acting like a Reddit clone, I think that questions on Steemit could easily act like a Quora clone. If questions do really take off, we should see a pretty strong surge of curation rewards in the questions' child posts.

In answer to your related question: I don't think a child post can be more valuable than the parent. I read somewhere that the value shown on a parent post is the sum of its own value and all its children/grandchildren. But maybe we need to wait for a dev to come along and confirm!