I'll use my friend Scott Snyder as an example here (and I'm about to repeat his name a lot). Scott's first hit was on American Vampire with Stephen King. Immediately, Scott is labeled as a horror writer because that's what Stephen is. As Vampire continued without Stephen (it's Scott's book, after all), Scott's branding went from "working with King" to "Scott is a horror writer in his own right". Aware of his branding, Scott has been careful to select projects that fit his brand. Swamp Thing, Severed, and Batman are all books with a horror twist. It's easier for him to get these books because DC and Scott know what Scott's brand is. His brand is so clear, in fact, that he has to be careful of what he works on in the future. Skipping around without regard to what books suit him would hurt Scott. I suppose Scott could write Spider Man one day (Scott can do anything well), and if it ever comes time for him to tackle the web-slinger, I think Scott knows that he has to approach it very carefully because Spidey's not known as a horror book. Scott isn't doing well because he's lucky--Scott also pays attention.
As artists, we still have a brand. And even though we all need to pay bills, we shouldn't say yes to everything. Your brand is built by the titles you produce, the characters you've drawn, the writers you're associated with, the vibe of your art, and by your blogs and tweets. Figure out what your brand is and use that to dictate your decisions. Even if you're on a book that's not quite "you", perhaps you can suggest something to the writer to help inject your brand into the story. I didn't think of Joe the Barbarian as being within my brand, but making it really dark helped me move it closer to my brand. American Vampire SOTF is totally my brand; PRJ will be the purist form of my brand.