1976-1985 Mercedes-Benz W123 Series
^IMHO non-biased opinion. What makes a good car? It's not how fast it goes to 100 km/h but the internal qualities. The W123 was solid, reliable, well-built and brought its occupants from A to B in style and comfort. It was practical, fuel efficient (for that time, excluding the 250, 280 and 280E models) and had "performance" (again, for its time). This car IMO is without question the best German car ever built. This is also the car which got me to become a Mercedes fan.^
One magazine called it "Without doubt, the best saloon car of the 20th century."