Utrecht said:
In my mind, that is why the Demi-Humans work, because while not strickly human, they are human enought that we can "act" the part with little to no difficulty.
Indeed. Psychology is derived from how you perceive and interact with the world, which is, in turn, derived from your physiology. Humans and demi-humans will have more in common than they have differences. But the more exotic you get, it's going to become impossible to get into their head. (i.e. the jellyfish critters: No head to get into. But more on that later.)
Take lizardmen: They're reasonably similar to us. Bipedal, similar senses, superficially similar environment. Tell me. Has anyone explored the physiological and psychological effects of having a pineal eye in a sentient species? Shouldn't they have very rigid circadian rhythms? Can they not become psions because their third eye actually is outside? Not to mention that they have an amphibious lifestyle. That would alter their psychology as well. But even if we can't truly answer these questions, with anthropomorphic animal races, we at least have a baseline cultural expectation of what their psychology and behavior should be like (from our skewed primate perspective, of course).
Now bring back the jellyfish. Not only are they not bipedal, they have entirely different sensory and nervous systems, and they're radially symmetrical. Their psychology would be
completely different. How does a player get a handle on this? Most likely, all they have to go on is the blurb the authors of that setting or race provided, so you get either 1) a bunch of jellyfish PCs who are all exactly the same, as per the book, OR 2) A bunch of human psychologies in jellyfish bodies (which is exactly what a lot of people are complaining about with demi-humans).
How is this "more creative" than using the demi-humans? It's superficially creative ("I look different and have different physical capabilities") rather than actually interesting ("I
am different in the way I perceive the world and how I interact with it.)
The problem is not the races, it's the way people tend to play them. Start giving out substantial experience bonuses for playing the race of the character in a substantial way. While you may be getting human psychologies in elf bodies now, I think you'll have better luck getting players into an elvish or dwarvish mindset than an invertebrate one. At least they'll have cultural, literary, and physiologic perspectives to draw on.