Hmm... I've never seen NGE.
As for Higurashi, Iwatched it with my sister to convert her. She loved it, but she still doesn't like watching anime.
I agree with Yu Yu Hakusho. That's the first anime I ever watched. Fullmetal Alchemist is also enough to make someone an otaku. Both seasons of that show are fantastic.
But what really won me over was He Is My Master, which was the first anime I ever watched through downloading means.