Acting is, of course, such an integral component to a film. At its core, it can make or break a work. It's what can divide the line between good and bad. Can you think of any truly great films, however, that have largely mediocre/average acting in your books? There's a few for me.
Halloween - cringeworthy acting aside, it's a technical gem. The framing, direction, and editing rank up there as some of the best 1970s American cinemea spawned. This can be applied to most of Carpenter's work - he doesn't seem to pursue much of a grasp for screenwriting or casting, unfortunately, but he's one of the most visually impressive filmmakers in his respective genre.
A Man Escaped - even though Bresson's deliberate hire of non-professional actors was supposed to spawn a sense of 'humanistic authenticity', I thought the acting in this film was particularly low-key. With that being said, Bresson simply was a wizard with the camera and knew how to put a film together. There is a reason Bergman, Tarkovsky and Kubrick spoke so highly of him.
2001: A Space Odyssey - the acting is hardly anything to ride home about, but the rest of the work surely is. It's probably the single greatest artistic and technical achievement in the history of the medium.
Night of the Living Dead - the mostly substandard acting should have been a huge detriment to this film, but Romero somehow managed to overcome that with his incredible skill for storytelling.
Elephant - this is one of my very favourite films. I can't say that the acting is too impressive, however. With that being said, this was a 'directors film'. Long takes, orgasmic tracking shots, and some incredible use of sound. Editorially, it's remarkable, too. Van Sant was at the top of his game with this one.
The Texas Chain Saw Massacre - typical horror movie acting in this one, but Hooper still managed to create something truly perturbing as a whole. It's probably the most radical and extreme of horror films that employs a lot of 'art-house' conventions.
Mirror - this is one of those rare films where the acting actually seems secondary. It's strictly a visual experience, and the acting, whilst far from bad, hardly spawned anything memorable. I can not say the same about Stalker or Ivan's Childhood - Tarkovsky exceeds in all facets there.
White Dog - The acting is rather choppy in this one, but it's saved by Fuller's amazing technical direction and his adept ability to tell a political film without speaking of politics at all.
Those are just a few. Your additions?