Years ahead of its time, this is basically the Hill Street Blues of medical dramas. Launching the careers of the likes of Denzel Washington, David Morse, Mark Harmon and Howie Mandel, storylines range from dramatic to trivial, challenging to funny to sad, and it treats the viewer as somebody who can retain multiple story arcs in their heads at the same time. It also has one of the most famous series finales of all time.
For the discerning viewer, there are also any number of in-jokes and references to other TV shows and pop culture, such as Dr Mark Craig mentioning that he was a colleague of MASH's B.J. Hunnicutt in Korea. Also listen out for the staff announcements in the hospital that are "paging Gwyneth"-- St.Elsewhere was exec produced by Bruce Paltrow, and Gwyneth was his then six-year-old daughter.
Several other subsequent TV shows since have included references to St.Elsewhere, such as Nurse Carol Grace in Oz (written by Tom Fontana, who also wrote for St.Elsewhere) having come from St.Eligius in Boston.