I chose myths (Greek in particular), although they're only part of the triad of elements from my early life the kick-started me on the fantasy route. Those other two things were an interest in dinosaurs (especially a love for "Lost World" scenarios), and a love of Godzilla movies. Because of those three things, I was attracted to monsters at an early age. Monsters are what originally got me into DnD and fantasy as a whole; I remember wanting to get a copy of the Fiend Folio when I was 4, just because of all the monsters, but my parents wouldn't buy it cause the early 80s was the height of the "work of the devil" craze. Of course this led me to Nintendo RPGs, reading my dad's old copies of The Hobbit and LOTR, and eventually DnD itself (started on the old Red Box).
So there ya go. Mythology, dinosaurs, and Godzilla.