Difficult question -I would have to say between three -Colour Purple (did not realise this was one of his) which was brilliant, ET which was gorgeous, and Close encounters of the Third Kind.
I am going for my VERY favourite as Close Encounters as it is a film I have seen at least 3 times which is something very rare for me, followed closely by ET which I have also seen 2 or possibly 3 times and which still makes me cry each time I watch it.