During the decade of the 80's, I was between the ages of 0 and 10.
Keeping this in mind, the movies with the largest impact for me, and which bring me back the most nostalgic memories of the 80's are:
1. The Goonies - I recently revisited this classic. Didn't realize how much foul language there was in this. It's got such a great 80's feel to it, and it reminds me of the little adventures I used to go on with my friends.
2. E.T. - My first alien movie, and what a doozie. The Halloween scene just transports me back in time, Reese's Pieces advertising and all.
3. Explorers - The 80's era for kids was all about NASA and space exploration. Until the unfortunate and catastrophic Challenger incident. This was an awesome movie for kids in the 80's, with plenty of 80's charm and nostalgia. It also features a very young Ethan Hawke and River Phoenix.
4. Conan the Barbarian - My first R-rated movie! My dad let me and my brother watch this with him, with the caveat that we have to cover our eyes when he said so. This movie was and still is great. It takes itself very seriously, and in doing so avoids the pitfalls of extreme cheesiness.
Other movies with that extreme 80's feel: Beverly Hills Cop, Back to the Future, The Golden Child, Top Gun, The Dark Crystal, The Black Hole (technically 70's), Ferris Bueller's Day Off, Pee-Wee's Big Adventure