What It Takes for a Movie to Be No. 1

Barely a month into its theatrical run, "Avatar" set a record for world-wide ticket sales, topping $1.85 billion. That is a reflection of its wide popularity, and also a reminder of the quirky way that Hollywood crowns champions.

In recent decades, the agreed-upon benchmark for movie dominance has been box-office revenue, unadjusted for inflation. That means "Avatar," like the previous all-time leader, 1997's "Titanic," and prior box-office kings benefited in part from favorable comparisons. Since...