I'd probably go with Sean Malone, but it should be noted that I'm a huge fanboy.
The man possesses technical superiority and aesthetic appeal that is second to none among all the bass/stick players I've ever had the pleasure of listening to - including (but not limited to) Anthony Jackson, Michael Manning, Victor Wooten, Steve DiGiorgio, Bill Dickens, Lars Norberg, Pete Perez, Tony Levin, Billy Sheehan, etc..
His sense of dynamics is tuned to perfection, and he has an uncanny ability to turn an otherwise plain piece of music into an incredible aural experience with his always tasteful note choice and beautiful tone. He does not overplay, and he doesn't go off on wild tangents from the remainder of the band. At the same time, his bass presence is constantly huge and his bass lines are very busy, generally acting as another melodic force that raises the recording to a whole other level of tightness and coherency.
He has shown compositional skill with his Gordian Knot project (granted, the second one was seriously lacking). He has done his fair share of Jaco worship.. and IMO, has surpassed the guy. He has played in prominent ways within a variety of styles, including technical metal, progressive fusion, various forms of jazz, and on many other recordings as a session musician. He teaches University level Music Theory while working on his own Ph.D in the field (actually, I think he already has it). He has had papers and articles published on music theory and knowledge. He has offered up presentations on music theory at various reputable conferences.. and I believe he's even put out a book or two on the subject of bass, one of which is filled with detailed analyses of some of Jaco Pastorius' greatest solos.
And, of course, he was a defining member of Cynic - the band that put out only one 8-song album, disappeared, and changed the world of metal forever.
Oh yeah, and his fretless soloing is just.. mm.