best bass guitarist? I'd say Hellborg. Wooten is faster and flashier, but Hellborg is proficient at Indian Rhythm, in addition to being able to play anything else. John Mclaughlin is the best guitarist i have ever seen, and Hellborg can hang with him and percussionists like Selvaganesh, which is almost superhuman.
Jaco was one of the best, but people have stood on his giant shoulders. If Jaco were alive, he'd probably be the best ever.
Upright bass I have to go with Edgar Meyer. Watching him solo is a thing of beauty.
Although Chris Wood is not in contention, I have to give him props for when i saw him in a bass battle with Victor Wooten, and Wooten was playing slap BG and Wood on upright, and Wood destroyed him. It wasn't a competition per se, they were playing together (actually is was the flecktones and medeski Martin and Wood all on stage jamming) but Wood I think knew who he was playing with and had to bring his A game.