Over the past 25 years, there have been a lot of fast sedans from at least half a dozen carmakers, mostly from Europe. But one series consistently leads the pack in power, sophistication, dynamics, and yes, even affordability (relatively). That series: the BMW M5.
E28 (1984 to 1987)
The E28 got the M5 ball rolling. With a detuned twin cam inline six from the M1 mated to a 535i chassis, BMW gave the world the first M5. It became the fastest sedan in the world. Even by today's standards, almost a quarter of a century later, it is fast-- 60 mph in 6.2 seconds. A top speed of 153 miles per hour.
E34 (1988 to 1995)
BMW continued the tradition with the E34. They continued to be hand built. Legend has it that BMW's test drivers could tell which team built which cars because they all handled and performed slightly differently. To see how they perform under real life situations, look no further than the one featured in Ronin. It put the venerable 450SEL 6.9 and the newer S8 to shame.
E39 (1998 to 2003)
Of all the M5s, I coveted this more than any other. When it first came out, a guy who worked on the same floor as me had one. He admitted, sheepishly, that he never took it over 80 mph. Only decorum and grace kept me from slapping this guy in the face. Sacrilege! BMW will build better and faster M5s in five year increments, forever. But this will always be my favorite.
E60 (2006 to the present)
I know little about the latest iteration of the M5. Chris Bangle's influence (or mangling) is obvious. The performance numbers are impressive. For the overly paranoid or environmentally conscious, a dial offers 300, 400, or 500 hp on tap. There is an argument that there are so many gadgets and computer aids in this car, the car loses touch with the driver. The connection between car and driver is the very essence of BMWs. Maybe the E60 marks the end of M5 uber alles.