There's no doubt about his contribution. It was all part of the band's evolution. From a bunch of friends playing skiffle to getting into the rock and roll bit, then taking it seriously enough to forge ahead. It has been pretty well documented that Pete had a loyal following, Ringo just fit in, he was the missing piece to the puzzle, and the four had that chemistry that made them The Beatles. Didn't matter if Ringo was a great drummer or not, it was the sum total that made them complete.
