Equal Sequel

What have Aliens, The Good Bad and the Ugly, The Empire Strikes Back, Godfather II and Henry V have in common?  The last two should give you a clue, seeing as they have numbers after them, and as far as I know there isn’t a Henry 1, 2, or 3rd out on DVD.  Although there is the Henry IV parts 1 and 2 and the three parts of Henry VI which were written before the Henry the 4ths, which isn’t at all confusing.  God knows what would have happened if the Godfather II would have taken...