Clapton fused blues and rock in an accessible and exciting manner. He also incorporated a fair deal of free jazz and metal theory in his solos, but his smooth playstyle made these sounds authentic and accessible. Clapton was the first guitar player to make the complex compatible with the public, and your dad probably talks about him every opportunity he gets.
Willie Nelson
The great Willie Nelson is one of the last true cowboys that made music for the people. Nelson was born in 1933 and he's still performing with the same energy he had when he was a kid. In fact, Willie has been performing for just over 60 years!