As a kid I used to watch the ones everyone was watching (DBZ, Pokémon, et al), then I pretty much stopped liking anime, then I actually began to DISlike it.
Later on, this and that happened, and I got into Doraemon, followed closely by Lucky Star. They were guilty pleasures at first, until I started getting into more series, then I just said "fuck it, I'm an anime fan now" and the rest is history.
Technically Doraemon was my "gateway drug", but I'd say it was Lucky Star that actually pushed me over the edge, so I give the credit to LS.