Quick! Name a Hollywood franchise that has produced its finest installment on the fifth try. It’s tough to do, right? Everything from “Harry Potter” to “Police Academy” tends to peter out after two or three films. But the burly, brawny “Fast Five” bucks the trend. By shifting into a previously untapped gear, it delivers the most entertaining “Fast and Furious” adventure while also getting 2011’s summer movie season off on the right lead foot.