Frankly, I'm sure the Beatles would have achieved the level of popularity they did without Ringo. What other drummer would have performed better?
Nor was he totally overshadowed though. He drew a lot of attention with the Beatles however more so as a personality than as a drummer.
Because he actually does have an amiable personality, I think the ultra hip and somewhat snotty rock music media of the day tended to give him the short shift as a drummer. I think he has garnered greater respect as a drummer over the years as peoples hindsight becomes more like 20/20.
The Beatles could not have achieved the success they have without a drummer that helped catalyze things and that's exactly what he did. He was a key ingredient in the soup and not overshadowed nearly as much as most good drummers out there probably.