Best decade? The 80s. No competition.
Best year? 1987
Adventures in Babysitting, *batteries not included, Beverly Hills Cop 2, Can't Buy Me Love, Death Wish 4, Dirty Dancing, Dragnet, Ernest Goes to Camp, Evil Dead 2, Fatal Attraction, Full Metal Jacket, Good Morning Vietnam, Harry and the Hendersons, Innerspace, La Bamba, Lethal Weapon, The Living Daylights, The Lost Boys, Man On Fire, Mannequin, Masters of the Universe, Moonstruck, Over the Top, Overboard, Planes Trains and Automobiles, Predator, The Princess Bride, The Principle, Project X, Raising Arizona, Revenge of the Nerds 2, RoboCop, The Running Man, The Secret of My Success, Some Kind of Wonderful, Spaceballs, Stakeout, Summer School, Three Men and a Baby, Throw Momma from the Train, The Untouchables, Wall Street, Who's That Girl, The Witches of Eastwick
God, I wish I had been old enough back then to go to the movies regularly.