1994 -- Ace Ventura: Pet Detective, The Mask, Dumb and Dumber, Clerks, Forrest Gump, Shawshank Redemption, Pulp Fiction, Natural Born Killers.
^^Not a bad lineup.
EDIT: Looking at another year -- 1999 was pretty damn good as well.
Matrix, Three Kings, Fight Club, Magnolia, Lock Stock and Two Smoking Barrels, Being John Malkovich, The Insider, Blair Witch Project, Toy Story 2, Any Given Sunday, Office Space, American Beauty, Sixth Sense.