Best is pretty subjective, and to be honest I do not think you can really lay that label on anyone, as there are just so many great players out there.
Its all a matter of taste I think. I know guys that think Jaco, Stanley, etc..are the best, but I get looked at like I have two heads when I say I cant really listen to guys like that, and prefer the likes of Phil Lesh, Jack Cassady, etc....