The first filmmaker I felt like I discovered for myself was François Truffaut. (Satyajit Ray doesn't really count because I grew up with his films on television and in my head since before I can even remember, so I have no recollection of ever "discovering" him).
In my late teens, Truffaut gave me my first taste of auteur cinema, and I've been a director-centered movie watcher ever since. About the same time, I happened upon two amazing books: James Monaco's The New Wave, and Annette Insdorf's Francois Truffaut. They taught me that simply watching films and responding to them intuitively is fine, but when you read what good writers have to say about films, it opens up a world of ideas that you can bring to every other film you watch for the rest of your life.
I pulled them off the shelf today and noticed how frayed they are, inscribed with excited marginalia, streaked with hieroglyphic drawings, and generously paved with highlights and underlines.
I haven't revisited a Truffaut film in several years, and I'm a little nervous that what once seemed revelatory and magical in the flush of my young Doinel years will now seem a bit less so. To be fair to Truffaut, there is a tendency among cinephiles to disparage him at the expense of some other and deservedly more eminent filmmakers, but I wonder if some of that isn't due to the broad renown he achieved that those directors didn't.
I'm pretty confident that my favorites (The 400 Blows, Shoot The Piano Player, The Story Of Adele H., The Wild Child) will remain undimmed by time. About some of the others, I'm not completely sure. I need to risk shattering the movie raptures of my teen years by returning to them to find out.