Update: on further reading of the Wikipedia entry (yes after writing this comment) I see that the rating that is relevant here is based on the critical response, not the public response. Which probably makes my comment below particularly off-topic. But critics are also consumers, although not usually paying customers.

I have a suspicion that consumer rating of artistic content is often a function of how well the marketing matches the content to the consumer who will most appreciate it. Little or no marketing for a niche product might actually produce a higher rating from a small enthusiastic viewership than for a highly marketed product that pulls in more consumers. Of course even those that rated the content lower probably spent money on it.

Why don't I recognize any of the titles? Do you have to be obscure to get 100%?

Because you have no idea about films.

I was initially sceptical, as eg the IMBD is heavily gamed towards populistic obscure cult films. But all the films in this list are indeed classics. I can really trust my profession, film critics.

These films are not the best of the best, but the classics. Which you can recommend to your grandma.

There are many very famous movies in that least, though perhaps not among the recent movies.