Skewl above is, of course, correct. The GSXR1000 and the Hayabusa and the Honda mouthful-of-alphamerics have been battling back and forth about the title of "fastest" for several years, but they are none of them the fastest, only the fastest PRODUCTION bike (defined as a run of so man units), depending on who you ask and what time of day the timing was done.
You are right, the Y2K (a handbuilt turbojet powered bike) is way faster than any of them, having no effective topend. It can just keep on accelerating until you take off or your wheels fly apart (whichever comes first).
Personally, I think cornering is at least as important as straightline speed, so my vote would go to Ducati, or perhaps Aprilia, for "speediest" if there were such a category, but there isn't.
Anyway, put the Guinness Book away and get out on the road. And try to keep it upright.