On the Billboard Hot 100, two can be the loneliest number. While having a No. 1 song can define an artist’s career, there’s far less glory in finishing one spot shy of the top slot. Yet some No. 2 hits have gone on to become classics. This month, Chris Molanphy looks at three songs that still loom large in our culture: “Shop Around” by the Miracles; “We Got the Beat” by the Go-Gos; and “Since U Been Gone” by Kelly Clarkson.