I'll second all the choices in the above post, they include what I'd recommend in the mobil products and amsoil has no flies on it either.
I wouldn't rule out a 20w50 if you're in a warm climate. However if Kawasaki only recommends a 15w50 as the heaviest oil, it's up to you whether you want to pay a premium for that oil as I think it's more limited in the manufacturers that offer it in a MC specific oil.
With that, I ran Mobil 1 15w50 "car oil" for well over 5,000 miles on an oci in my ZRX 1200 and it performed just as well as any other oil I've put through it in 81,000 mi. Only thing I would note, sheared down to a 40 weight during that interval, as a flashpoint of 400° showed no notable fuel contamination. If you go through motorcycle oil analysis, you'll find it three or four pages back. It says 4000 miles on the analysis however I left it in there for another 1500 or so after the sample.
I try different oils all the time as I'm more interested in what the oils offer for additive packages knowing that in the end the wear results are all going to be similar.