Best sounding?
Regis Laconi’s 2002 Aprilia RS3 Cube MotoGP bike. Damn that thing was mental! The engine was essentially just 3 cylinders from a Cosworth Formula 1 engine. I was at Donnington for the 2002 MotoGP, and though the bike was well off the pace of the front runners, it was totally insane. Popping, spitting and backfiring everytime the throttle was shut, making a noise more akin to God gargling than anything else! No silencing whatsoever, was the loudest MotoGP bike in the field by a country mile, so much so that following years they enforced a decibel limit I believe which led the Aprilia effort to end up getting axed only a couple of years on. But by god what a noise!
Last of the 990cc Ducati Desmosedici’s made a rather tasty noise too, and the roadbike is probably the best sounding roadbike available.
Of course you can’t beat a big Ducati twin either, the rumle of 2 enormous cylinders overlaid with the clattering of the Desmodromic top end and a rattly dry clutch, all make for a rather more colourful noise than any in line 4 crap!