Also a depressing one. What kind of retarded marketing department thinks "dragons don't sell"? It's a videogame! Nerds are all over that shit. Dragons only don't sell when the product they're in is otherwise crap. Heck, Divinity II first got my attention for the very shallow reason of "I get to turn into a dragon! Fuck yeah!"
Such research is likely based on how previous dragon games have sold, which is not good for the most part; however, that may have more to do with the quality of the games rather than being about dragons.