Racial preference pretty much only comes up on the internet on RPG boards, and I think that's a good thing. I'd rather it stayed in the realm of fantasy.
In every case I have seen, RPGs regard race as species... and may even get less specific than that.
As to Racial preferences, I think we need a radical variety and not some +1/-1 +3 uniformity of options. That we should start with the easily playable, readily understood races other than human is a given. Later on we should put the game engine and volunteering players to the test with wilder and more difficult ones.
Human - Default, right?
Elf - magic man, lives a long time, a lot of historic and literary descriptions actually exists here, but they are pseudo or demi-humans at best.
Otyugh - these things are smart, can talk, eat, and are relatively mobile. Not too difficult here, but we're going to want to ease into play for multiple reasons.
Carp - Below human intelligence minimums (afaik), can't walk, only swim, can't talk, and they breathe only water. Carp are hardly unknown to the D&D community or that fantastical of creatures, but they are still not a race most people will want to play for numerous reasons.
Giant Space Hamster - Who doesn't want to play one of these? They could be too large to get into most locations on the older end, but maybe they're intelligent, right? At least one guy thought he could communicate with one. Weapons are sort of limited as is most other equipment. This is the difficult case, almost playable, even enticingly so, but so many obstacles to play.
Ability to communicate with other players is going to be a big hurdle. Ability to move at relatively the same speed is another too (not too fast or too slow). Ability scores so far beyond the others that no one else matters in that respect? Or so far below the others they are hampered in D&D adventures? Size can get out of hand too (too tiny or too massive). Variety is awesome, but extraordinary differences often lead to problems.
In the end, if polymorph is going to mean anything, or race is going to mean anything beyond Star Trekian "aliens" which are all virtually humans with odd, yet poorly fleshed out cultures, then we're going to want a vast variety across the board statistically, but also an understanding of the hardships deviating from the norm entails.