D&D was my first exposure to "traditional fantasy", when I was ten.
I'm not kidding: I grew up reading old-school science fiction like Isaac Asimov, as well as Greek and Egyptian mythology, but I had literally never heard of elves or dwarves until I picked up the "red box" Basic Set (in the single-volume UK edition). Because my father didn't read fantasy, my mother didn't read genre fiction, and I was the oldest child, there simply was no fantasy in the house until I got into the game.
(Well, no, that's sort of a lie. I'd heard of dwarves, and read some fantasy, because I had read the Chronicles of Narnia, but given that Narnia blended fairytale talking animals with mythological creatures, when you think about it those dwarves kind of stand out. Still, there was nothing resembling Tolkien or Howard or any of those classic fantasy writers in the house.)
Anyway, I picked up D&D because I'd seen it mentioned in the novelisation of E.T. The Extra-Terrestrial. I guess it kept my attention just because it was something new, and yet familiar at the same time: I'd never heard of elves or halflings or clerics, but there were plenty of mythological monsters whose names I did recognise: hydras, harpies, minotaurs, et cetera.