The only basic criteria it needs to meet is that I dug it in some way. I love some movies with both terrible sc<x>ripts and bad acting, but I like them because I enjoy them.
both: 70% acting and 50% sc<x>ript =))
Except the 20% excess.
Both! Plus good director, cameramen, editor and money!
Good acting can make the worst sc<x>ript into an good movie.