Basically, no race that is a tough challenge due to something inherent like strength, size, natural or supernatural abilities etc. should IMO be reduced to the power level of humans and other core races.
Definitely agree. In the 1E DMG Gary Gygax devoted a notable amount of space to this general idea. There's a whole section titled, "The Monster as a Player Character". It is actually in that section where he talks about the game being "humanocentric".
Right up front he suggests that it's a questionable idea because the motivation that players have in wanting to play "monsters" as their PC is simply to dominate the campaign. He then notes that the game orients around humans for good reasons and suggests that there's nothing particularly wrong with some experimentation along these lines but that in the long run it should be humans and demi-humans that REMAIN the focus of the game. His conclusion however comes down to: if you want to allow monsters as player characters that's YOUR problem.
Now when he's talking about "monsters" he's talking about them in a far more general, 1st Edition style (since this is FROM 1E). He mentions demons, devils, demi-gods, undead, and dragons as being common requests from players but I'm pretty sure that he'd heartily lump creatures like Drow, faerie races, giants/half-giants, and the like into that broad category of "monsters".
I have to agree with his sentiments. Always have. Now it's been my fortune that my players have rarely, if ever, asked to step any distance outside the bounds of what the PH or a particular campaign settings' sourcebook lists as a PC race. I've come to see that as both good and bad. Good, because it means that I have been spared a lot of headaches stepping on the necks of players who are trying only to disrupt my game to satisfy their own lust for lording it over the other PC's and myself as DM. Bad, because I think there's a lot of
fun to be had in playing as or alongside a character who is highly unique simply due to being a wildly outrageous and nonstandard race. But a request to play an UNusual race can't exist if there isn't a roster of USUAL races to refer to.
We should all step outside the box a few times and exercise our own imaginations and challenge that of our DM's by playing a PC of an non-standard even downright exotic race. But, approval for that should still rest with the DM and it should not be a matter of OVERRULING the PH to say, "That race is too wierd, too powerful, too newly invented to be included in my game by default and so it is forbidden except by special request." It should be a matter of acceeding to SPECIAL requests to play races as PC's which are NOT "traditional", even generic and staid fantasy stereotypes.
Unusual, powerful, and newly invented races belong in supplements or as campaign setting design choices left STRICTLY up to the DM to allow as he sees fit. Words like "standard", "generic", and, "default" when applied to choice of races that are appropriate for inclusion in a Players Handbook simply do NOT allow for dragonborn, drow, eladrin, tiefilings, half-giants, undead, lycanthropes, aasimar, githyanki, warforged and many others. Let the game designers field their SETTING design ideas forward in some other, more appropriate place. Even the DMG would be an appropriate place for including some alternative PC race possibilities that just don't belong in the PH - if accompanied by firm assertions that their use by players is subject to DM approval for all the above reasons, and thus well-considered by the DM for those reasons before being allowed, and NEVER to be assumed as a
right by players.
But that's probably just me.