Quite regularly one of the top 3 grossing movies of the year is a family friendly animated movie that is released in the summer and/or holiday season. The reason for this is simple, at these times durring the year parents take their chidren to see movies (or send their chidren to the movies) because they're out of school and it is something to do which isn't that expensive. Typically it is a Disney, Pixar or Dreamworks animation (mostly only Shrek series) that has done this well.
On top of this, I have expectations that the many of the movies you listed (Transformers 3, Harry Potter, and Pirates of the Caribbean) may not do nearly as well as other titles in their series. Pirates of the Caribbean already saw declines with the third movie from people being disappointed with the second movie, and I suspect it will see further declines from people being disappointed with the third; and Transformers will probably see the same kind of pattern, with people who were disappointed with the second avoiding the third. With Harry Potter, I think the "battle" will be between people who are growing tired of the series and those that were disappointed with the latest installment vs. those that feel an obligation to see this installment because it is the last Harry Potter movie.
