My parents showed me this movie when I was about 4-5 years old. It is one of my first life memories as well, just not in a good way! The ET character freaked me out, my parents kept trying to reassure me it was "friendly" but I wasn't buying it. Anyways, I was hiding behind a bunch of pillows on the couch the entire movie and I had nightmares about him for years after. I have never been able to force myself to watch it again, and probably never will. Even as an adult, the sight of it gives me the creeps.
Maybe I was an overly sensitive 5 year old, but I would wait a few more years to show it to a child.