It's not nearly as basic as you think. In SOME of the songs (likely the ones you've heard on your local radio station) the song structures themselves were "simple" but they used a read and react improvisational approach most of the time in performing their songs where the guitar runs would reach outside the standard pentatonic playing of say Clapton, and move into relative keys and modes like Jazz, only with a rock based feel. Jerry also often used a chordal outlining approach in some solos, much like a keyboardist or a banjo player, creating a very melodic feel. In these cases the band would react to his lead by supplementing alternate chords or voicings as they went.