Saxy_jag has it exactly right.
I am a writer for 'Drummer' magazine, and we all know that Ringo is one of the fiest back-beat drummers in the world, and a major influence - including his son Zac who is a superb player.
John was probably exercising his famously caustic wit with his throwaway comment, which stuck - not that Ringo was at all bothered I'm sure.
Although - if you listen to 'The Ballad Of John And Yoko', you will hear the excellent drumming skills of Mr McCartney. Ringo was away filming 'The Magic Christian', and George was on holiday. so Lennon and McCartney worked on the record themselves - Macca on bass and drums, and Lennon on lead and rhythm. A fine record - but hey, Ringo was the drummer in The Beatles, and his work stands the test of time for anyone who knows anything about drums.