I used to have a 2006 Kawasaki ZX-6R and the best MPG I saw with that was 49.5 -- it was on a roadtrip up the PA turnpike to my buddies place. My other friend was driving in his car too, he drives like an old lady so that forced me to keep it pretty darn close to the speed limit. It started to rain along the way and I had to go up and over a mountain.
Here's a picture.
I have a 2008 Kawasaki ZX-10R now and the best I've seen is 38 mpg.