Keep in mind that "successful software developer" is a fuzzy term. You can be a successful developer if you are gluing APIs together for an internal enterprise web app and making six figures per annum. You can also be an unsuccessful developer in those same circumstances, if your ambitions are different.

The "CS focused people" that you typically hear about usually have Ph.D.s because you usually hear about (and from) people doing fancy new things. There are many other "CS focused people" out there just keeping the lights on, or rather keeping the backbone routers from being swamped under their own routing tables.