There is now a clear consensus over which motion picture was No. 1 at the box office this weekend. Sly Stallone's action holdover The Expendables for Lionsgate is the easy winner after a nailbiter Friday. It was followed closely by a newcomer, another of those cheap Fox spoofs, Vampires Suck, which opened Wednesday. In fact, the order of the entire Top 10 kept changing more than usual day to day because no studio could agree on the grosses. In all, there were 5, count 'em, new films opening in North America to almost close out the summer. Yet none of them could break $12.5M by end of Sunday.