Truth: I would rather listen to the people Robert Johnson has inspired than listen to the man himself. Also true: Keith Richards makes me want to dust off Johnson and give him another listen. I saw Under The Influence on Netflix.
"Rock and Roll had nothing on these guys" -- Keith Richards on American Country Music in general and Johnny Cash and Carl Perkins in particular.
Yeah , but there was a time when The Rolling Stones were particularly scary. Read Sway for some idea. And Keef is big on going straight to the source. Robert Johnson didn't record much, so The Centennial Collection should do you. Plus you get a spiffy essay by Jimmy Page. If you can find it I recommend The Sun Years by Howlin' Wolf. And I recommend the recently rebuffed Damn Right, I've Got The Blues by Buddy Guy -- the album that turned everything around (for Buddy Guy, of course).