When they came out, they were Rock 'n' Roll. Starting with songs like "Please Mr. Postman" "Blue Suede Shoes" and a variety of other rockabilly tunes by guys from the 50's. They had their original material, "Eight Days A Week," "No Reply," and "She Loves You," which were POP tunes...and of their many different styles of playing....it's generally the pop/Top 40 genre that the Beatles are classified under.
They did pretty much anything....classically influenced stuff like "Penny Lane" or "Yesterday." "Stoner" or Acid rock like "Strawberry Fields" "Sgt. Peppers Lonely Hearts Club Band," or "Lucy In The Sky With Diamonds" (an acronym for LSD) to any other of the other styles they could/did pull off at a moments notice.
I'm a die-hard Beatles fan, but Rock was a genre that came after the Beatles appeared on the scene.
Though they lacked total output in their catalog, you could have added "Cream" to the list too.