What are some quality dramatic films that were marred by mediocre/bad acting?

A lot of people seem to point to Keanu in Dracula or Sofia Coppola in Godfather III (see the commonality?), but I'd have to say Ryan O'Neal's unconvincing turn as a tragic opportunist kept Barry Lyndon from becoming a breathtaking masterpiece. It still is a great, great film that I loved watching, but O'Neal's timid, half-ass accented acting constantly prevented me from being mesmerized by the movie itself. In fact, I'm wondering if he provided the only mediocre acting in any of Kubrick's movies.