
Do you think there are more or less (or the same) new superheroes being created now for the Big Two than in the past?
I think there are less, and for two possible reasons:
1. It's seen as a better business strategy to concentrate, for the most part, on building the brands they have. Superman, Spider-Man, Green Lantern, Batman, etc. Solo books launched with brand new superheroes tend to not do as well. The "real-estate" on team books are at a premium -- while you can have one or two new characters, most have to be established. And "third tier" new characters created specifically to round out superhero teams have a very spotty success rate (Vibe, Gilgamesh, or Manitou Raven, anyone? Anyone?).
2. Many comic creators these days are hesitant (loathe?) to "give away" their best ideas if they are not going to have a healthy rights share in them. This is not always the case -- but it is indeed some of the case. An exception to this "rule" would be someone like Dan Slott, who is like a new character factory.

In a broader sense, the playing field for characters might be so swollen as it is (just look at the old Who's Whos and Marvel Universe Handbooks to catch a glimpse of some of it), that there is no pressing need to create superheroes in the frequency of the 1960s or 1980s/90s. Also, there are tons of new characters debuting -- from the other publishers, and from self-publishing.
Personally, while it is far too early in my career to really speculate, I'm 50/50 on the creating new characters thing. I'm fine with creating new characters, and I'm fine with "donating" (though I'm really being paid) some of my "pet" ideas to books and projects where I do not control 100% of the rights. I think it's good to give something back, and to contribute new and viable things back into the pool of ideas that gave me so much pleasure as a young person.
On the other hand, I have several elaborate ideas and projects that I'd want to have more control over. For example, I have a long narrative and whole world built in my vampire novel, with hundreds of new characters. I've worked a long time on building that elaborate world and writing that book, and it is also intensely personal to me. This may not be a property that would be ideal to sell a portion or all of my rights to. This may be something I would want to put out myself. But the caveat is, by putting it out all myself I lack the exposure and market penetration that a major publisher would give me. I mean, through my own self-promotion efforts I might get a lot done, but it just doesn't compare.
I don't think that in terms of expanding the Marvel & DC Universes, full-creator's rights is an ideal set-up. Just having characters in the same book with different rights tiers can be problematic, especially for reprints and adaptations in other media. I've seen the complications first-hand that such arrangements bring.
By the same token, I understand the need of comic creators to own their own characters and control their destinies. I don't think there is an easy or ideal solution, and I think all those solutions will involve some degree of compromise one way or another. But while I think it is OK for the major comic publishers to not produce so many new characters as they did in the past, it's always good to invest in tomorrow's "stars." Remember, characters like Wolverine & Lobo were flukes. And they might already be in those new comics, on the stands right now, waiting to capture the imagination of a new generation...
What superheroes and other characters created in the last couple of years from DC and Marvel do you think are tomorrow's stars?
