This is more of an opinion than an encyclopedia-style entry, so I'm putting it here -- but Starr's main contribution was his laconic humor. The Beatles were as much about personality and charm as they were about music, and Starr was one-fourth of that. To simply focus on the songwriting does him a disservice, and misrepresents the band. Lots of English guys had musical and songwriting talent, but only four of them became the Beatles.
Favorite Ringo line: during a United States tour, he was asked, "How do you find America?" Starr replied, "Turn left at Greenland." - RjLesch
Are you sure? AHDN predate the big breakthrough in the US doesn't it. I certainly don't recall that line of dialogue. -- GWO