IMHO, Lesh is the best bassist ever of ANY genre - jazz, rock, or blues. Perhaps some do not consider the Grateful Dead a "rock" band, but Lesh is in a class all by himself, IMO. He's capable both of incredible technical skill and dexterity, but in addition to that, did incredibly innovative things in bass playing.
I am also a big Chris Squire and Tony Levin and John Paul Jones fan. But Lesh stands above these, and all the others, IMO.