Of all time? Alone in the Dark. No, I don't mean that 2005 train wreck. I mean the 1982 one starring Donald Pleasance, Marin Landau, Dwight Schultz, and other well known B movie character actors. The movie is not flawless, but the first 30 minutes was so good that I was willing to put with the crap the final hour of it.
Of the last year, Donner Pass is right up there. It is a well paced horror movie that reminds me of 80s and early 90s horror. The plot is formula, and you can pretty much tell who is the monster about 15 minutes after you meet him. What sold it for me was the dialog and character development. The 4 characters you meet at the beginning of the movie has completely developed story arcs by the end of it. The movie does a goods job of making me feel something for the characters.