I got to number 19 before finding one that I hadn't seen. Atonement, and watched it after having been intrigued by it for years but never giving it a go. What a wonderful movie. At the end I sat through the credits in silence. Am now going to watch number 33 as that's the next one I haven't seen. ( Not counting Vertigo but I may have seen that when I was a kid. Will watch it another time. ) Gone Baby Gone certainly doesn't sound uplifting.
I don't know, I think The Sixth Sense (1808) is a few years older.