[retyping because the browser ditched my post...
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IMO many cool monsters are getting watered down by too many options around, most notably the abuse of subraces (not anymore), half-races and loss of character restrictions.
Having a race of half-dragon is cool and can be a great addition to a setting. Having any possible combination between a dragon (any type) and another creature, means you're going to see a half-black half-gnome, then a half-gold half-minotaur, then another and another, then you have draconic bloodlines, and dragon-blooded sorcerers... at some point there are so many around that it's not so special anymore to be a half-dragon. [thank god, dragons are the most resilient D&D monster, so they STILL ARE totally cool!
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Elves got their share with too many subraces (a trend finally over). If you have high elves, wild elves, aquatic elves, dark elves, sun elves, wood elves etc. in your game, what is still left about "being an elf" is not a strong archetype.
Drow are a cool race with very distinctive features. So kewl that people wanted to play one! Here starts the loss of restrictions, which takes away the "uniqueness" of drows. But after all, why having only evil drow priestesses and wizards, why not having also good drow rangers? And when you're tired of good drow rangers, why not a lawful half-celestial half-illithid half-drow monk with vow of poverty? However, do this over and over and it's not so special anymore to be a drow. After all, the lawful half-celestial half-illithid half-drow monk with vow of poverty is not really "more drow" than a lawful half-celestial half-illithid half-human monk with vow of poverty.
edit: So I have basically answered that I agree that Elves and especially Drow are IMXP the once who lost most appeal.
Now I also add that oddly the Elves have got a little help from the fact that half-elves suck, otherwise they'll be more half- than full- elves
