Robert Downey Jr. in 'Iron Man 2'There's no question that 'Iron Man 2' will be the unstoppable box office victor of the first weekend of the summer. The only question is: how big will its victory be? Will it be big enough to break the opening-weekend record of $158.2 million set two years ago by 'The Dark Knight'?

In 'Iron Man's' favor: It's the sequel to a huge critical and commercial hit. It's the first big movie of the summer. It faces no real challenges from other new movies. It's opening on a record-busting 4,380 screens. One hundred eighty two of them are IMAX screens, so 'Iron Man' can count on some hefty surcharges. It has Robert Downey Jr., whose bankability has greatly increased since the first 'Iron Man' two years ago. It has a $100 million marketing campaign. It has appeal to all demographic groups, not just young fanboys. It has the continued comeback of Mickey Rourke, as a buff villain. Oh, and it has Scarlett Johansson in a catsuit.