Look at it another way; BMW leads the race and holds that lead for a long time. Then Audi shows up (late) with their competitor. This gives BMW the opportunity to develop the next gen M5 into a even better car than the Audi.
And, how many magazines have chosen the Audi over the M5? Regardless of more HP. It's the total package and driving dynamics that makes BMW excel. How can Audi get the same handling when they have a big engine hanging in front of the front wheels???