I never knew who Cliff Burton was until a few years ago. Admittedly I really like his work and Connie really works at advancing his image. She frequently brings unknown pics and clips of her brother to light. Back to topic here. If he was best we will never know. I find his solo's were unique and his playing style fit in very well with the mix. It wasn't lost or overpowered the other instruments. Part of that was his choice of instrument. The Aria Pro II was a very nasally mid-range instrument. So metallica sonically was drums for the bottom end, bass for the mid-range and guitar for the top end. Many three or four piece bands neglect the mid-range. Most bassists choose a very bassy pickup and they run the risk of getting lost in the mix with the drums. Maybe Cliff could predict the future because on Jason Newsteds first outing with Metallica Lars Ulrich insisted on burying the bass playing. A mid-range bass would have fit better and not have been a threat to Lars. Cliff showed promise to be one of the greats but to be a great I think there needs to be an extensive body of work to compare with others. That is just not there.