Most people seem to pick elves for the infravision or to be multi-classed, but I don't feel the need to tie myself to Tolkien's Pentagenea. I think that if you're going to play an elf, you need to be an elf. You need to consider that your long life makes all your friends just pets in your world. You can be fond of them, but they're bound to die anyways. Which always seems a bit out of place. Half-elves? They're just an excuse to get around restrictions.
Dwarves? OK I love a good dwarf fighter, "You orc? Me kill," and who doesn't like a bit of gold greed on occasion. Yet that gets weary.
Halflings? Can't get excited about them. They're always thieves is seems. If they aren't, you always kind of ask, so why a halfling?
Half-orc? I find the half-orc a breath of fresh air. However, in most campaigns it's bordering on playing a humanoid to play one. Nobody ever likes you and it can be central to a campaign. It's a bit weird being everyone's bad guy, but as mentioned refreshing.
Gnome? I like the gnome, just because it's not from Tolkien. You're sort of a dwarf, but magical. I have fond memories of really playing an illusionist gnome once.
I've played the wilder strains, where everyone is a freak, yet eventually I come back to humans.
I feel the human by not being so defined allows the player to be most expansive. He's not defined so much by his race. He's a slate upon which you can create anything, unconstrained.