Don't really know for sure, but here are the contenders:
Something's Gotta Give
Jaws
Out of Africa
Wizard of Oz
Many Disney flicks (for example...when my daughter was 3 she watched Snow White EVERY DAY, then Toy story, then Beauty and the Beast ... you get the idea)
I'm sure there are more on this list, but just can't think of more right now..
But the one movie I've probably seen the most is Ferris Bueller's Day Off. When I was a teen my friends and I watched it so many times we could recite the lines. I haven't seen in a few years now, though.
I got myself a Toto. Wait - you had a Toto, too, didn't you? LolI forgot about The Wizard of Oz, it might be number 1