I think he was crucial to the Beatles. He's not on my Mt. Rushmore of greatest drummers (Bonham, Peart, Portnoy, Collins) but he's perhaps the greatest drummer for the Beatles. It was pointless to be Ginger Baker in the Beatles, that's not the kind of band they were. They weren't improvisers, they weren't jammers, they weren't about the sort of "music as a journey in and of itself" like Crimson, or the Dead, or Cream. Sort of coincidentally, Eric Clapton himself recognized that later when Harrison invited him along to help smooth tensions between the other members.
I think Paul McCartney is the single greatest living musician on the planet right now, and he was part of the collective that actively chose Ringo Starr to further his and John's vision. I'm also a big fan of the idea of "chemistry" in a band, and I think when you have a two-headed monster like Lennon/McCartney, you NEEDED a guy like Ringo, a "shut up and play" kind of guy, to make the team work.