For me it had to be "Matrix" , as I remember at the time it totally blew me away ,before it came out there was not another movie that could compare to it as far as effects were concerned .
I also owe that film a huge debt of thanks , I used to work in electrical retail and back in the day when dolby pro-logic first came out for TV's I used to almost be guaranteed a sale when I used the clip of Neo and Trinity storming the office building to save Morpheus to demonstrate it to customers. It was literally a case of play that scene, turn the volume up , and when it had finished the customers were saying "where do I sign? I want one now! ", so from that 1 movie clip alone I earned hundreds of pounds !