Two of Motown’s greatest groups shared the stage at the Seneca Niagara Events Center for a night of pure classic soul. The Four Tops and the Temptations together represented decades of ‘My Girl,’ ‘I Can’t Help Myself,’ ‘Papa Was a Rollin’ Stone,’ and ‘Reach Out I’ll Be There’ — a catalog that defined a generation. The Niagara Falls casino crowd got one of the great package tours of the classic R&B era.