I am so feeling my age. Most of these so-called childhood films came out when I was a teenager.
The two films I most remember loving when I was very little were films I saw at the library (they had screenings on 16mm on the weekends). I was still in kindergarten.
The Red Balloon
and
Winter of the Witch
The first was the story of a boy and a balloon that follows him around the streets of Paris. The other is the story of a boy and his mom who move into a house that has a witch. The witch makes them magic blueberry pancakes that make them happy. We used to act this out in my friend's basement.
Other films that I remember loving as a kid were ones that would appear on The Wonderful World of Disney (VHS wasn't available yet so it was TV that allowed the possibility of seeing things more than once). The original Freaky Friday (with Jodi Foster), the Kurt Russell teen films -- The Computer Wore Tennis Shoes, Now You See Him, Now You Don't and The Strongest Man in the World (these were the stories of Dexter Reily, a science geek, and his science mishaps).
I'd also have to include the three original Star Wars films (though I was a teen by the time the last one came out) and most definitely...
Raiders of the Lost Ark
This film, more than any other made me want to get involved in the film and television industry.