The Beatles are my favorite group, but I'd have to vote for Jazz (including Soul Jazz, Funk Jazz, Rock Jazz, Latin Jazz, Traditional, etc. Mostly late sixties/early seventies). People who like classic rock would thoroughly enjoy the work of guys like Dennis Coffey and Jimmy Caravan. The former did a cover of "Whole Lotta Love" with guitar riffs that are just devastating. Mark The 45 King sampled the drum breakdown on that one, which of course is just flawless. And Beatles covers? There are so many!
My second favorite form of music would have to be Reggae (Strictly instrumentals, including Soul Reggae, Dub Reggae, Roots Reggae, etc. Mostly late sixties to mid seventies).
But I can't vote for either one