It's a head-to-head showdown between two leading athletic apparel businesses.Nike (NKE 0.77%) is the undisputed leader when it comes to sports apparel and footwear. But its share price, which has climbed a disappointing 2% in the past five years (as of Aug. 20), resembles anything but peak performance.The Oregon-based company's struggles have opened the door for a business like Lululemon (LULU 1.94%) to rapidly rise up the ranks in the industry. But the athleisure pioneer has seen its shares tank an alarmin ...