The matrix for sure, it really did put a whole new spin on in movie special effects. Absolute magic.
Star wars also, it has been adopted in SO many countries, and is so widely recognised as a revolutionary film. From the concept of an all seeing all doing force, to absolutely magnificent action scenes, and a heightened sense of reality no other space movie had had, this movie really set the bar a notch higher. Lucas created his own universe from the bottom up, and never had this been done to such extent before