The purpose of presenting a "basic repertoire" is two-fold. First, it provides a convenient subset of classical works that a new listener may want to explore to further develop and refine their musical tastes. Second, it provides a "road map" to related works that even a seasoned classical music lover might have missed.
The list is definitely not meant to be a comprehensive listing of all worthy compositions, or even of just those worth exploring. There are many, many gifted composers who are not listed here, and there are many works by well-known composers that are of great value, but not listed here. This list is meant to be a starting point, not a definitive listing of all great works.
Acknowledgement
Thanks to Todd McComb, Christopher Brewster, Jim Plank, Marc San Soucie, Vance Maverick, Bill Cutler, and countless others for their invaluable assistance with suggestions for additions and changes to this list over the years.