Well, I started to flatly disagree with my pal Jeff about that. In my mind, James Jamerson was the first electric bass virtuoso, and the first true innovator, on the instrument in music history. Jack Bruce was the first bass virtuoso in rock music history.
But then I thought it prudent to check out the dates of key recordings before shooting my mouth off.
I'm not familiar with Jack Bruce's work before December, 1966, which was the release date of "Fresh Cream." So I'm taking that as a benchmark. Then, looking at the discography of Motown, I find that Jamerson had turned regularly to the electric bass before that date and had, by then, created the bass tracks on I Can't Help Myself, You Can't Hurry Love, Uptight (Everything's Alright) and perhaps most significantly, Reach Out I'll Be There." His greatest work was still ahead of him. Of course, so was Jack Bruce's.
I still lean toward Jamerson. But I suppose it doesn't much matter when considering two such colossal innovators.
With the other things Jeff says, I agree. Especially the part about the "marvelously diverse and harmonically rich music" on Jack's solo albums. And I must add a word about his superb and utterly distinctive vocalizations. What a great talent he was!