Definitely the greatest. Long story short, BMW doesn't make them like they used to. Don't get me wrong, I'm a huge fan of BMW's new M-cars, but theres just something missing...
I realize that we all bond with our cars as we drive them and get to know them better with time. If you ask me, I think the E39 M5 is not only one of the greatest M5s out there, I think its one of the greatest sedans ever produced. With BMW jumping on the turbo bandwagon with its newest generation of M-cars, I appreciate the prehistoric 5.0L V8 under the hood of the E39 M5 now more than ever. Sure, I hardly get more than 20mpg on the highway, but who buys a high-performance V8 sports car for fuel economy anyway? The amount of torque on tap at low revs is fantastic, and means you never really have to wind the car out to accelerate quickly.
I always feel that the E39 generation has aged really well. For a car that went out of production over a decade ago, the car still looks fresh. With the quad-tailpipes and subtly-aggressive bodywork, I know that this M5 will always look the part no matter how many new generations come out. The interior has always been a fantastic place to be, with leather everywhere and a suede headliner that oozes sporty-luxuriousness... Im sure thats what the designers were going for.
This is a sports car you build a relationship with, a car that takes some time to get to know. Most importantly however is the fact that the car can go from a sensible everyday cruiser to an all-out tire shredding hoon monster at the push of two buttons (those being the SPORT and DSC OFF buttons of course). This car aims to please, and has honestly never let me down. While I absolutely love driving the E30 and E36 M3s we also have at home, the E39 M5 will always be the reliable choice to get me to wherever I want to go in the upmost comfort.
Best BMW ever? No, that has to be the E30 M3.
Best BMW sedan ever? Quite possibly.