I figure there are two distinctions of "great bow"
One is craftsmanship related as in joinery, fit, finish, glue lines, fadeouts, symetry etc.
The other is performance related as in speed, cast, quietness, stability and general shootability.
Most bowyers seem to say that almost everything is a tradeoff. For example, most say that making a bow really fast usually makes it less stable or forgiving.
I've also heard some very good bowyers say that there is no one thing rather a lot of little things that give 1 or 2 FPS here and there but if you incorporate 5 things that make the bow only 2 FPS (each) faster you have a whole 10 FPS more speed which is quite significant. It's things like limb material, design, mass, shape, riser length, reflex, deflex etc.
I figure you could spend a lifetime chasing changes that give more speed without sacrificing stability and come up with a pretty nice bow....
The Jack Howard Gamemaster bows and Adcocks ACS bows are good examples of this. So are Morrisons and Fedoras.