What has Steve Harris innovated? People often site his "galloping style" which really isn't that big a deal IMO.
Cliff Burton; What has he innovated and what makes him so creative? Burton is IMO one of the most overrated bassists on the list and owes his notoriety to being Being with Metallica and the fact that died in a bus crash.
Hamm; IMO by far the most versatile and technically skilled of any you mentioned due to his capability to play a wide variety of music and being one the best solo bass players around. He also is IMO much more creative than Harris or Burton. When compared to Deacon, Deacon may be more creative in a band setting but Hamm of course excels as a solo player.
That is why these break downs can get tricky as so much is subjective. Two IMO fairly knowledgeable people like you and I can look at the same player and have completely different opinions unless the difference is really obvious. Maybe when players are so close they could be bunched together and rated, for example, 25a, 25b, 25c.
For the record, I subscribe to Bassfreak's philosophy that criteria breakdowns should basically be used to roughly order the list, but they won't necessarily be the final list result, other things (what I like calling intangibles) have to come into play too in terms of doing final list ordering.
Steve Harris' 'innovation' lies in popularizing and widely using the galloping style (first person to widely use it), but it goes further: he was the first big metal bandleader who also was the band's bassist (should that count toward his placement here???), he is THE guy responsible for keeping flatwounds alive in the modern era (and showing that they can be used much more widely than just in pop/rock and roots rock, I mean he played them in speedy metal and made it work), and most importantly he was metal's second great bassist chronologically, after Geezer (it's worth noting he was the FIRST great bassist metal had seen SINCE Geezer in the early/mid 70s), and was the first 'lead bassist' in metal.
Burton is a bass god in my book, and challenges Claypool for a spot in the top 5 most creative players ever in rock (in my mind, PROBABLY Jamerson/Macca/Claypool/Flea/Squire in some order, though Squire's definitely #1). The problem is that given that he's inaudible in 75% of his recorded material with Metallica (albums), it's hard to discern what he's doing most of the time on record, though even on the albums you can hear Anesthesia fully, all of his playing on the Kill Em All album, his distorted ventures on 'Call of Ktulu', the octaved bass intro to 'Damage Inc', the distorted solo in 'Orion', and other defining moments of his career, as well as occasionally his main playing (when songs get softer, like the first half of Sanitarium, the first half of Fade to Black, the interlude in Master, etc). Listening closely and attentively to the bass parts, where audible, on the Ride and Master albums starts revealing the extent of his genius...to appreciate him fully though you have to go on youtube and listen to the remixes people have made of those songs with the original bass track boosted (courtesy of Guitar Hero: Metallica separating the tracks and boosting the bass level immensely). It's a revelation and absolutely blew my mind. His melodic subtlety, sensitivity, and note choice are on the level of Macca and Flea; he's as harmonically ambitious and sophisticated as Macca, Flea, Jamerson and Squire; and he pushes the use of distortion and effects further, with artistic merit, than any other bassist I've heard, he basically invented a 'school' of effects use and approach to distortion. No, he didn't live long enough to fully mature as a musician and refine his playing, but his genius is abundant in terms of the things I've mentioned, note choice/placement, use of the bass as a composed part of the song (like in Baroque music, his favorite genre of music), use of the bass as a countermelodic instrument by way of genius harmonic play off the guitar line. He helped push bass soloing into a completely new direction, too, and integrate solo spots into full band (all instruments) songs brilliantly. This isn't even to mention that he was BY FAR the most musically ambitious and advanced metal bassist of his generation, and more ambitious and musically advanced than any metal bassist before him. Metal bass playing can be basically divided into a 'Before Cliff' and 'After Cliff', he's the god of the genre and unanimously praised by players in metal to this day as a, or THE, primary inspiration on their playing in the genre. He was classically trained and used the bass as a thru-composed 'voice', harmonically countermelodic, in what were by and large fairly standard metal song arrangements, which was totally unprecedented and has never really been replicated since (note that the next generation of great metal bassists, like Patterson, DiGiorgio and Choy, their innovations were in using jazz/fusion style in metal songs; Cliff was the singular figure who used a classical approach, and one worthy of the classical masters, in metal songs).
Hamm is a good example to my mind of a guy whose technique and knowledge of the fretboard and internalized knowledge of scalar patterns, arpeggios and intervals are all exceptional, especially for rock, but whose actual CREATIVITY (what he DOES with all that knowledge/ability) is not on the level of the best (Macca, Jamerson, Entwistle, Flea, Claypool, Squire, Burton, Sheehan, Levin, Deacon). He's composed some outstanding solo bass pieces and deserves credit for moving that forward as an art. Creativity he doesn't touch Burton or Deacon, sorry. I'd say Harris beats him in creativity too, though maybe only slightly.
As far as ordering goes, yea its tricky, that's why this 18-28 stretch of the list is taking so long...! But it's fun! And thanks for bein' around to help me figure all this out