TL/DR: it depends.
Lots of good suggestions here, but it's ultimately impossible to give a definitive answer. Great chops + great restraint belong somewhere near the top of the list. Ability to play all styles and all techniques? Depends on how you define "great." A better approach might be to ask what makes a particular great bass player great. I love Lee Sklar's playing, but he's on record as saying he can't slap and doesn't care to learn. He'll recommend another bassist if the gig requires slapping. But he has some awesome chops and the good sense not to demonstrate them 99% of the time. His chops manifest themselves in his always being on the money, timewise, and he knows his instrument so intimately that he's able to go where his feel dictates without having to consciously figure out how to get there.
I love Chuck Rainey's playing, because he's always full of surprises that, once you've heard them, seem like the only possible place there was to go. His playing on Steely Dan stuff is absolute genius and really makes the groove. In my car I keep an old Joe Cocker cd (I can Stand a Little Rain) and Rainey's playing on "I Get Mad" is just sublime. I crank it when I'm on the highway alone, and then I look down at the dash and see I'm doing 95 mph.
Jaco is one of the greatest, for chops and innovation, if not restraint. He borrowed from other innovators like Rocco Prestia and Jamerson and fused it with non-bassist like Charlie Parker and created something that hadn't existed before, that ended up influencing a whole new generation of bassist. There are so many examples out there of him holding down the bottom while playing incredibly lyrical and harmonic lines. Restraint is not one of his signature qualities, though, and I would probably not hire him to do a classic country gig
Lots of great players, and every one of them is great in a different combination of ways. As many have said, taste (which IMHO is 90% restraint) is key. Chops need to be adequate for what the player is doing, but I wouldn't put them at the top of the list. Versatility is good, but I think Duck Dunn was one of the greats, and I don't know of him venturing far outside the R&B/Blues-rock vein. Pino, on the other hand...that guy seems to be able to do it all without breaking a sweat. Lyrical fretless stuff, slap, fingerstyle funk, jazz, you name it. Maybe not as innovative as a Jaco or Prestia or McCartney, but took things from them and forged something that is simultaneously his own sound and completely serving the song. He raises everything he plays on to a higher level. Maybe that's the best definition I can come up with: the ability to raise a song to a higher level than it was, without taking it over.