Yeah, I have to say that I thought I read that post wrong at first. One of the things that people praise about Image is their diversity and not being just superhero books. Look at their most recent series:
Mind the Gap
Thief of Thieves
Luther Strode (only kinda a superhero book)
America's Got Powers
The Red Wing
L'il Depressed Boy
No Place Like Home
Out of that whole list of recent or upcoming books only 3 of them are superhero books. And out of the older books only Invincible, Savage Dragon, and a couple of the Extreme books are really superhero books. The other Extreme books are sci-fi and other older books like Spawn, Witchblade, The Darkness, Hack/Slash, etc I consider more horror and supernatural than superhero. So I'm perplexed by that poster's assertion.
My assertion is based on longevity more than quantity. I'm not interested solely in the types of concepts that Image will greenlight, but which ones have managed to build a long term audience and have become consistent sales leaders over time. Of the books you listed here, most of them have been launched quite recently. In order to evaluate a concepts viability, we have to look at it over a defined period.
The standard I'm using to define success is subjective but I think it's fair:
Books that have lasted 12 issues or more
Books that have lasted 24 issues or more
Books that have lasted 36 issues or more
The more issues of a book that are published, the more successful it has been. The higher you go in terms of consecutive issues published the more superhero comics dominate the offerings.
Books like Spawn, Chew, Savage Dragon, Invincible, Walking Dead, Darkness, Witchblade anchor Images market share. Of these, I would classify them all as superhero comics aside from the Walking Dead and Chew, although some use horror motifs, they still operate within the spectrum of the traditional superhero conceit... superhuman abilities, recurring antagonists, moral and ethical code, a predictable pattern of social behavior, etc.
Of that list of books that were characterized as praiseworthy for there diversity, how many will be around in a year? In six months? Well, obviously I can't say precisely, all the metrics I've looked at would indicate the following factors are most prevalent in a successful Image book.
1. A visually distinct character(s) with unique abilities (all successful Image books have a main character or characters that you cheer for, they also have superpowers or effect some permutation of that quality).
2. Maintaining the publishing schedule (All of the most successful Image books get the work done in a timely manner with consistent quality. I think that's this Kirkman's greatest strength; his books come out regularly).
3. Conceptual viability (making the initial draw of "Prankenstein" develop beyond Punk'd for monsters).
When compared head to head, superheroes seem to recover better from failures in these areas than other books.
If my professional objective is to create a book that has sustained market value then I have to look at the books that have achieved that state over the last twenty years; past is prologue, after all. In twenty years from now, things may be different but not as yet.