You overestimate Mercedes-Benz, as simple as that. The company needs someone younger as a chairman. BMW is leading now with a lot of engines choices, has diversified its offer earlier than MB, which has lead to an increase in sales, topping MB as a number 1 worldwide.
MB is still on the top, in some things still well ahead the rivals, but in others clearly behind. A few decades ago it was always well ahead.
Based on what I´ve been told and been reading, MB knows this quite well, and things should change for the better in a few years, with the launch of new top end models, the expansion of AMG as a stand alone division (more unique AMG models) and the low end models pushed upmarket (C-Class range).
I think by 2015-2016, things should be better for MB, as some investments will see their return.