Wally Cleaver makes a valid point. Ringo was not always the drummer on record. Paul McCartney provided many of the drum parts, particularly in the latter part of their collective career. At one point, Ringo even got tired of being excluded from the process, and walked out in disgust... but he returned with his hat in his hand, so to speak, the next day (pride is pride, but come on... we're talking about the Beatles here).
In the early days, Brian Epstein voiced his objections about replacing Pete Best with Ringo. No one, not even Ringo himself, doubted the fact that Best was a much better drummer technically. But Lennon and McCartney were adamant. With regard to Pete Best, as Lennon said, "He's not a Beatle."
That being said, let me just say that I think the world of Ringo. When he did play, which was most of the time, he played with a lot of "feel," and a lot of heart. Yes, the beat fluxuated slightly, but with the exception of dance tracks, it is supposed to. A good classical piece with a perfect meter would sound completely lifeless. Look at any serious score, and you will see instructions for changing the meter during the piece.
Ringo's contribution to the overall experience, however, goes much deeper than a steady beat or a flashy fill. One of the things that attracted George Martin to them was not their songs, but their "confidence and cheekyness." No doubt, they were all extremely charismatic, which drew a lot of people to them. All four players had "star quality" (as kids, who among us didn't want to be "a Beatle" while watching "A Hard Day's Night?").
I'd be the first to admit that, ultimately, it was the music that mattered. But it was that star quality that got so many people to listen in the first place. Lennon and McCartney clearly knew what they wanted in a drummer, and considering the results, I'd have to say that they made a damned fine choice.