Lots of good points by lots of people.
I agree that D&D, as it is designed to be played, is not G&G, because, as others have noted, clerics and other spellcasting stuff and encounter levels make it pretty easy to become powerful enough to be able to afford to raise people from the dead. If death is an inconvenience and not a real fear, that's not G&G. And if 10 1st-level guys with bows aimed at you don't scare your character, that's not G&G.
That said, I also think that a lot of G&G is flavor-text. I've said it before, I'm sure I'll say it again: D&D is an abstract game, and if you do a really dumb version of flavor-text, it's easy to get a result you don't like. That doesn't make the rules stupid. That makes your flavor-text stupid.
For example:
The event: A 6th-level fighter (currently at 34/57 hit points) has just finished off his opponent, only to see an enemy wizard cast a fireball at him. The fighter makes his Reflex save with a lucky roll and only takes 14 points of damage, taking him from 34 to 20.
If I wanted: Superheroic
I would say: The fireball hits the fighter square in the chest and explodes massively. When the smoke clears, the fighter is there, scorched but still standing. He shakes his head, wipes off his face, and says, "Ouch. Now let's see what I can do to you."
If I wanted: Swashbuckling
I would say: The fireball streaks in and explodes, sending gouts of flame streaking in all directions. The fighter leaps acrobatically through the air, dodging most of the gouts of flame as they burst out, and lands with a few tiny scorch makes, his blade levelled at the enemy wizard. "You'll have to do better than that," he calls out.
If I wanted: Grim & Gritty
I would say: As the fighter sees the fireball streaking in, he shouts "Incoming!" and dives behind a tree for cover. He doesn't quite make it, and a wave of heat sears his leg as he rolls behind cover. His boot-leather sears his leg, and he knows the skin underneath is raw and angry -- and will likely come away with the boot when he takes it off. His lungs burn briefly as he inhales smoke and scorching air, but he knows that the wizard won't wait, and he stumbles back out, his panicked adrenaline rush keeping his leg from slowing him down at least for now, and shouts a scream of defiance at the wizard with his sword raised.
Same game, same mechanics, three different styles.
In terms of house rules I'd use to keep things scary:
1) Really come down hard on magical items. Keep wealth low, more potions and scrolls, very few permanent magical items.
2) If you keep healing magic, have it convert to subdual, not remove entiretly.
3) Turn the caster-ability-score requirement for spells so that instead of the ability score having to be at least equal to 10+spell level, the ability MODIFIER has to be at least equal to the spell level. This lets dragons and demons cast horrible spells, but most mortals never get past third or fourth-level spells.
4) d20 Modern massive damage threshold (Con score, Fort save to avoid dropping to -1).
5) When you get to half hit points, you take a -2 on all d20 rolls. When you get to one quarter hit points, that increases to -4.
If you do those four things, without making any other changes, then wizard or cleric pretty much becomes part of a multiclass combination, heals don't just put people back on their feet in mid-fight, and ten guys with bows aimed at you are still a threat. Even if they're only second level, there's always the chance for a crit, and with less magical stuff, you're much more likely to be hittable.