As was pointed out in the previous post about homebuilts, there are an awful lot of really 'nice' bikes out there - not great at anything, but pretty darn good at lots of things.
I had the pleasure of borrowing a Honda CB500F a couple of years ago for a weekend. That, and others like the EX650 series from Kawasaki or the FJs from Yamaha are what we used to call (sometimes derisively) UJMs - Universal Japanese Motorcycles.
Sneer if you like, but you'll never build anything this good in your back yard. I promise.