Jimi Hendrix:

Making rock music a much more complex and "harder" genre to box in...He (the American) also took the blues back from his white British guitar peers and turned it on its head, to the point that Clapton changed his sound to a more white, country sound by the early 70s...

David Bowie:

He injected "performance art" into music beyond anything that the Beatles or Jim Morrison was taking it...That means songs done in character (Ziggy Stardust, the Thin White Duke, The DJ, ec...) and each song taking on the personality of said character...The reflective, spacey tone of Ziggy...The funky, plastic soul of the Duke...In this way, Bowie could survive in music without ever being himself (see Madonna)...

Rakim:

More lyrically, than musically...Rakim was the first MC to write a song as a secondary character...Take say, "Eric B. For President"...Rakim turns the mic into a living character and becomes an afterthought: "I came in the door, I said it before
I never let the mic magnatize me no more...But it's biting me, fighting me, inviting me to rhyme..."

As I said in a old post about Rakim's impact, rappers were not doing this in 85/86...This was still the era of Run DMC and LL: very B-Boy...Rakim brought a surreal self awareness to writing when it came to hip-hop...Everything changed from that...

I could do more...but I would be here all day...lol