What makes an anime a classic? I remember when one of Hayao Miyazaki's films came out, it was considered a new classic. What makes the anime a new classic.
... Is this regarding Howl's Moving Castle?

It was based on a classic fantasy novel (by Diana Wynne Jones) so maybe some people were actually referring it to a new take on a classic, or it was classic in the sense that people knew it was going to be a classic because the quality of that film was on that tier. Kind of like how in the same way Disney movies turn out to be classics even when a new film comes out because of it's rich history in making classic animated movies.