I did a project on him for my applied music class earlier this year but was never really to big into the stuff I heard by him..._until_ i picked up the anthology album. let me say this, holy shit! so good.
Mike Stern is really good too, definitely worth checking out!
im not a big jazz fan myself, but i have to respect jaco and what he did for his instrument, before him, bass was not only fretted(electric that is), but more of a backround instrument
the common phrase is "jaco invented the fretless bass, and then taught us how to play it"
everyone should listen to 'portrait of tracy', pushes was bass can do/sound like