Based on the comments so far, these are what people are saying should qualify as the "Best Monthly Comic on the Stands Now that All-Star Superman Has Ended":
Justice Society of America
Comic Book Comics
I Kill Giants
Invincible Iron Man
Captain Britain and MI13
I would rank six of those in my current top 10. Some of the others, not so much. But all excellent suggestions! Is your favorite comic not on the list yet? What is it?
(And yes, one of the comics above would indeed get my vote for Best Current Monthly Comic. Which one, though???)