It certainly isn't as entertaining as some of his others, but the basis of Shadow of a Doubt is the perfect Hitchcock formula and was apparently his favourite. It's a story about a normal family dealing with a horrible murderer, which is what he loved the idea of: murder on your own doorstep. As you watch these films, note how often the hero is a normal person, thrust into an extraordinary situation.
I can't help but think that the two guys planning the murders for fun represent Hitchcock himself!