I agree that Criterion as a holy canon of movies is absurd mostly because taste is so subjective. My love for Criterion comes from their dedication to providing a quality product: the transfers are crystal clear, the sound is amazing, the special features are edifying and not mere P.R., and the physical package this all comes in is detailed and gorgeous. (My recent favorite art is Sean Phillips' cover for 12 Angry Men. If you like that, check out his work with Ed Brubaker in some of the best crime comics ever.)
While a great movie is a great movie whether on bare bones DVD or Criterion blu-ray, I really prize a set more when I know that the people putting it together appreciate the art involved as much as I do.