"If you’d asked me several years ago, I likely would have spoken about some tipping point where you have too much and everything crashed. Part of that is that I grew up in a world where there was one X-MEN book, one AVENGERS book and, well, three SPIDER-MAN books (counting MARVEL TEAM-UP.) But today, I think that, while there is a tipping point potentially somewhere out there on the horizon, it’s nowhere near as close as we sometimes like to think (or fear.) What matters is the quality of the work. How many BATMAN books are there at this point, every month? How many WOLVERINE books? And still, those characters are more likely to sell better than, I don’t know, THE FLASH or STORM. The audience likes what it likes, and so long as what you produce is good, they will always be content to have more. It’s when the quality goes down that you have a problem — but you have that problem with there being only one book as well."
-- Tom Brevoort, Marvel’s senior vice president of publishing, responding to a question on his Formspring about how to address character "oversaturation," if it's even an issue that exists