Seriously, I get the feeling many younger film fans these days seem to assume Pixar invented the perfectly balanced family film - you know the one that entertains the kids and the adults equally and maybe even squeezes out a tear by the end.
Harry and the Hendersons hits all these marks beautifully in my opinion. It also has a wonderfully warm, big hearted turn from Lithgow (the sort of role he's never had much of a chance to do what with all his snarling creepy villains and off the wall comedic characters), to the point its one of my favorite of his performances.
A criminally under-rated family flick these days. I've shown it to my niece and nephew and it still works just as perfectly as when my dad took us to see it on the big screen when I was a boy.