the all time best bassist of a rock band

[Lynch]

My quick list (no particular order):

Geezer Butler (Black Sabbath)
Billy Sheehan (Steve Vai, Mr Big)
Stu Hamm (Joe Satriani)
Steve Harris (Iron Maiden)
Les Claypool (Primus)
Chris Squire (Yes)
Jack Bruce (Cream)
John Entwistle (The Who)
Paul McCartney (do I really need to list anything here?)
Geddy Lee (Rush)
Roger Clover (Deep Purple, Whitesnake)
Bootsy Collins (Funkadelic)
Victor Wooten

 

[Aktivator]

Jaco would be my pick

others not mentioned
Percy Jones-Brian Eno and Brand X
Tony Levin of king Crimson, Peter Gabriel, solo, session