I'm personally fascinated with non humanoid characters, especially as the protagonist or playable characters, yet find so few games including or staring such. Typically these characters, if they exist at all, are isolated to juvenile games, or relegated to extras and supporting characters.

I've heard some of the reasons why this is common place, but it's all gotten a bit distant over the years, I was wondering if there are any story writers or students of psychology that could review the difficulties and barriers involved in these types of characters.

I'm personally a huge fan of the Okami games, and characters like Dragons are far more interesting to me than humans or humanoids, yet games tend to put poor effort into fantastic characters, or they just fail to earn despite critical acclaim. What's the deal...

I know of a certain hedgehog that did quite well in games....

My neighbor two doors down is a father of 3 in his mid thirties, ranked in the top 300 worldwide in EA golf online, a big shooter fan, as well as NBA 2K and madden, and I'll stop by and what's he playing?

If you happen to be familiar with personality type theory, I think this is the easiest way to explain why some people lack interest in some types of playable characters such as non-humans, or in other cases there are people who like traditional fantasy creatures but reject new mixes. The personality type S vs. N is the relevant one. N, which stands for intuitive, corresponds with people who like surprising and exotic things. They are more interested in the big picture than in details, and are more broadly creative. These are the kind of people interested in new and different kinds of playable characters, though sometimes they will be strongly in the mood for a particular type of character and reject others. The other type is S, which stands for Sensing. These people are known for liking traditional things. They are more interested in details, and their brand of creativity is mainly aimed at varying details; they may be unwelcoming to big-picture changes. They have difficulty imagining what it would be like to play an avatar type that they haven't played something similar to it before, and may have difficulty sympathizing with characters who are too far from humans, though they may be fine with familiar animals fantasy creatures, and fantasy races, such as dogs, cats, dragons, and elves.

So, a big part of many games, especially action-adventure games is getting the player to identify with the player character. While there are a lot of techniques to this, one that is often taken for granted is making the main character humanoid, just like the player. Certainly there are diversions from that, as you said, but generally... people see themselves as people, and then because of that, there are considerable resources dedicated to and designed to make playable humanoids possible, and a lot of people in the industry have experience and skills in playable humanoids. Playable, say, quadrupeds? Not so much. In fact, many of the design assumptions you might have, from object interaction, to talking to NPCs to who knows what, all go out the window.

I think Okami did something really marvelous, and it worked, psychologically, for two major reasons. 1) It was about the gameplay. Okami would have lost much of its charm in different genres, but as an action puzzler the character is already abstracted to a tool. 2) It was a highly stylized world, and based on a well-known myth, so there was a lot of freedom to explore that concept. 3) It was a canine, and many players are used to humanizing and empathizing with canines (sometimes better than other people). Add to that her cat-like agility, another familiar domesticated animal, and Okami has a familiarity that isn't TOO far off from a humanoid.

The other barriers, I suspect are that playable animals are associated with "kids stuff" and if not that, with the "Furry" culture, which is, among other things, overly-sexualized.

I mean, I'd be intrigued about a game where you play as a dragon, instead of a guy with a dragon, but what, exactly would be the gameplay? You're not platforming. You're not performing combos. You're not getting ambushed by rival factions. Or are you?