I define influencing pop culture as causing a global change in music, fashion, film etc tastes. Every artist has influences, but not all iconic artists propelled a change in the entire look and feel of a time like Elvis did and The Beatles did.
You're kind of mixing up what actually happened, Elvis, MJ and the beatles where not breaking new ground, the undergound music scene already had the clothing and haircuts, the beatles for example where not creating a new scene just bringing a scene to the mainstream, same as NWA/Public Enemy, and many of the Early DJ's, yes they have all been influenced by those before them but they didn't 'create' the scene.
As an example, Nirvana will go down as cultural icon, great individual talent but the fashion, music etc was already there long before it became 'fashion', same with NWA/Public enemy and 'just listening to car alarms' dance music that was shunned from the BBC.
What's being remembered as being a cultural shift is just "when did said generational shift" become commercialised.
In a few years some Grime etc artist will make it huge and make us all feel old, they won't be the ones who 'had' the most cultural impact though, it will be those highly commercial ones who became mainstream.
I get I'm sounding a bit snobbish, not wanting to, I used to be a free party dj in the early 90's and still has my music and dj name brought up (humblebrag)