The overwhelming popularity of the E39 M5 spawned a generation of imitators trying to achieve the same formula of success. You can see the aftermath of this as every major car manufacturer is focusing on the sports sedan market segment to develop a 4-door super sedan to rival the M5.
The other cars on the list are simply sports cars that are expected to be fast and expensive but impractical for daily use. The M5 was unexpected for its time merging family sedan practicality with Nürburgring-tested motorsports performance.
The E39 M5 is the perfect daily driver for me, and that is why I got one. The list is kind of silly, though. The cars listed are so different and such different price ranges. These are the best cars FOR WHAT?? They never say anything about that. If I could pick, I would drive a Porsche or Audi R8 on a track, but prefer my E39 for a daily driver. I almost bought an Acura NSX for my daily, but was questioning it for daily duty for my purposes. My guess is most of the people making this list haven't driven most or any of the cars they voted on. Pointless, in my humble but accurate opinion. (But at least the Beast is on top!!!!!!)
The choices on the list are very peculiar. 8 out of the 10 are very contemporary and flashy, and then there are the 2 M5's? Looks like a bunch of young guys voted and a few of them either had or their dads owned M5's. There are some great German cars from before the contemporary era that should have made the list.