IME nothing beats the sound of a high-revving V-12, a Ferrari or Aston Martin, for instance. Second to that, the balanced burble of any properly designed V-8 motor is mighty sweet.
I've lived in places where on the handful of perfect summer days the rich people would take out their exotics, and I could enjoy. I also remember being passed by a "New Edge" ('99-'03) SVT Mustang that must have had an aftermarket exhaust on its 4-valve V-8, because it was sounding as good as any Ferrari V-12 that I've heard.
I do NOT like the noise from mild I-4 motors with a Helmholtz resonator trying (and failing) to add the bass notes that only a larger motor can give. I do like flat fours, though. Something in the balance of boxer motors that makes them more agreeable to the ear.
I had a customer who built racing cars using the Ford 2.3l SOHC motor. With a tri-Y exhaust and a hot cam, they sounded pretty nice...for an I-4 that is.