As my forum name might imply, I've spent a fair time trying to suck the essence of jaco out of his records but people like him aren't good because of the amount of notes they CAN play but because of the emotion, train of thought and feel the pieces they play and write have. I firmly believe that it's far more likely to see someone play chromatic fantasy faster than Jaco did (due ot the sophistication of modern bass playing techniques) than it is to ever see someone match the sensitivity in the '76 album version of Continuum and other similar tracks.
I have and never will get close to anything Victor Wooten has done, i've tried a few times at the "easier" bits of the 'A Show Of Hands' album. I just sit there for half an hour and end up saying to my self "you know what Ben, it'll take you a few years to get the techniques here down to a decent level of fluidity let alone get round to learning the piece 'as is'.........cuppa time?....I think so!" then go cry for a while.
edit....
"I think there is a point to be made here.
Many of these monster bass lines/solos are played by people in an improvised setting. Take Jaco's 'Havona'. He didn't have to 'learn' that bass line as he had constructed his lines around the tunes he had written and used a couple of dozen of his own stock licks. Anyone who has spent any length of time listening to Jaco will know that he, like all musicians, repeats himself over and over, using his own signature licks to leave his mark on a piece. But it is important to note that much of what he does is made up on the spot ('Teen Town' being an obvious exception). It is actually a lot harder to learn a passage that is played like that than it is to burn one of your own.
In a more conventional setting, someone like Bruce Foxton would have written a line that felt comfortable under his fingers and that he could play without too much difficulty. Noone in their right mind would compose a complex line for a song that he could pull off only 3/10 times. Someone once said 'amateurs practice until they get it right. Professionals practice until they can't get it wrong'. Geddy Lee plays that solo lick off 'YYZ' perfectly everytime. It can't be hard for him as a, he wrote it and b, he has played it 200 times a year ever since. But have you heard him crucify 'Girl From Ipanema'? Easiest song in the world and he f***s it up! Francis Prestia is known as THE finger style funk player but that's all he does. He can barely put together a jazz bass solo, probably can't play a fretless in tune and definately can't read music.
It is more important to play musically and to your strengths than it is to be able to execute every great line you have ever heard. Work on your technique, yes, but learn to play the music not the musicians! And don't get dispondent you can't pull off 'Red Right Returning' by Michael Manring. He probably can't play 'Ace of Spades' like Lemmy either (can you?)."
Very, very well said (Y). Music is a medium to be used for expression, not to be coppied from person to person IMO. But if u want to do something new, it's important know what's come before.