@whatjd, we must be about the same age ;-) . Though the pre-British Invasion Pop music was dismissed as disposable fluff by the mid-late-60’s counterculture and critics---who insisted on bands being primarily Blues-based---they were mistaken. Your two examples are proof: Gene Pitney was an incredible singer and songwriter, and Del Shannon’s 1982 comeback album was produced by Tom Petty, who was a big Shannon fan.
Early 60’s Pop music was written by some of the best songwriters of all time: Carole King & Gerry Goffin, Cynthia Weil & Barry Mann, Ellie Greenwich & Jeff Barry, Jerry Leiber & Mike Stoller, Burt Bacharach and Hal David, Otis Blackwell, Bert Berns, Bobby Darin, Doc Pomus & Mort Shuman, and Phil Spector. The first UK Beatles album was simply covers of early-60’s Pop hits, fer cryin’ out loud!
There was also Chuck Berry, The Everly Brothers, Roy Orbison (now THERE’S a singer!), Surf music, and what Rock ’n’ Roll historians call Garage Rock: Paul Revere & The Raiders ("Just Like Me" ROCKS!), The Sonics ("The Witch" sounds like The Ramones, but much more primitive and brutal), The Wailers (the classic "Louie Louie", which every band in America played), lots more. A great time in Pop music, imo far better than most from the 80’s, for example. The "New Romantics", anyone? ;-)