Performance numbers alone don't make a great car. It's the senses - touch, hearing, and sight, I think, which contribute to the overall magic of a BMW.
For me the magic of my 330 is that it is built FOR the human being. The car is an extension of the driver. I can always test the limits of the car by feel. I can feel and hear the exhaust note. The engine communicates by sound and feel. When the doors and trunk close, I can feel and hear them. No other car looks like a BMW. It's instantly recognized.
In my Honda, I was an extension of the car. The car set the limits. The exhaust note was bland, and the engine never let you know it was doing till it ran out of HP. The doors and trunk closed like a screen door. Take away the grill badges and it's hard to tell the difference between an Accord, Camry, Focus, etc. The Honda was effective but emotionless.
A BMW is unique in that it stirs the senses- touch, hearing, sight. Other cars are plain vanilla in that regard