Quick note on is he "the best bass player", since a few people have chimed in... I'm with the school of thoughts that claims you can't really compare musicians. Maybe you could establish some metrics to do so, such as speed, variety and execution of techniques, knowledge of scales, knowledge of theory, etc. The problem is there is no metric to measure other capital aspects of what being a good musician is, such as "soul", "connecting with other band members", "connecting with the audience", being original in your writing but not to the point of having no base in a given musical genre or tradition, etc. Especially for me, the whole question always hits the same wall: I find a guy like Neil Young to be a better guitar player than Eddy Van Halen. Technically speaking, of course Van Halen is much faster and his mastery of scales is way more impressive! Yet I find his music soulless. It's like watching fireworks: Impressive, but it doesn't talk to me. Oppositely, by strumming 3 chords, Neil Young will make me cry. And to further illustrate... If you want to gauge my personal proficiency, think maybe Adam Clayton or Simon Gallup. You know, solid, simple, steady, reliable with a good touch of presence and originality. I used to play in a rock band which I quit due to personal reasons. I went to see their 1st show with their new bassist. As the guy was warming up, I could hear him play scales and arpeggios at incredible speeds, slapping and all sorts of things I'd never do. I thought "Oh my god, now they'll think I was such a fraud the whole time!". Then the show started and the new guy just couldn't keep in place at all! He was soloing all over the place all the time with no consideration for what the songs required, ruining everything. That's when I realized technique and good musicianship are not synonyms. This said, I like to be prepared in case some mad dictator puts a gun to my temple one day and says: You gotta choose who is the best bass player of all times or die! Then I'll say Alain Caron.