I think there are a few really special actors (Hoffman being one), people who are truly gifted and command the screen, whose performance can make an average movie good and a good movie great. Many actors who get hired over and over are probably more reliable than anything else. Among living actors, I’d put Sean Penn, Denzel Washington, Daniel Day-Lewis, and Anthony Hopkins in the first-tier along with Helen Mirren, Laura Linney, Jessica Chastain, Cate Blanchett, and Michelle Williams. I’ve heard Viola Davis is excellent, but I haven’t seen her in anything other than Fences. Surely others in that group or just outside it that I haven’t seen enough to really have much of an opinion.