When I got into D&D, I had just started reading the Hobbit, Lord of the Rings, and the Once and Future King. furthermore, we had just started covering Greek mythology in English class, my drama elective class was doing Camelot, and I was already a fan of the Harryhausen Sinbad movies. And, at the time, there Holmes Basic.
What, currently, keeps me interested in D&D?
1) The settings. Greyhawk as presented by Gygax in Dragon, the GR Folio, and first GR boxed. The Forgotten Realms 1e boxed set with the 1e FR series of supplements and several of the 2e supplements. Darksun original box set, Al Quadim, Ravenloft: Realm of Terror boxed set, The Known World Gazetteers.
2) The demons and devils: Demogorgon, Orcus, Asmodeus, Geryon, etc.