There are three brands in Germany that have been the mass production car makers. Below we see the year, sales, position in the market and percentage of the market captured:
Opel took top spot two consecutive years in the early 70's but that didn't show on the list. VW slipped in market share over the years, but has fought back recently. Opel was a real threat to VW, but now battles to fend off premium brands. Ford has failed to keep its share and is outsold by all three German premium brands.
In summary: VW is not as good as the chart indicates, but it is the real German brand and that is patriotism. Opel has recently under invested while propping up GM North America and it shows. Ford is better than its position in Germany indicates, but it obviously suffers with its image to now be so low in market share.