- Season 15 | Er

While some viewers initially felt the show had lost its way in its later years, Season 15 is largely seen as a return to form—reclaiming its status as one of the best medical dramas in television history.

: The standout feature of this season is the return of original cast members. Fans were particularly moved by the guest appearances of icons like George Clooney (Doug Ross), Julianna Margulies (Carol Hathaway), and Anthony Edwards (Mark Greene), whose flashback episode, "Heal Thyself," is cited by viewers on Reddit as one of the series' best. ER - Season 15

The two-hour series finale, , is frequently hailed as a masterclass in how to end a long-running drama. Reviewers from IndieLondon gave the season a 5 out of 5 rating , noting that it successfully tied up loose ends for current characters while giving past favorites a meaningful "cherished" send-off. While some viewers initially felt the show had

: The return of Dr. John Carter as a series regular for a multi-episode arc provided a familiar anchor. His personal medical struggles and his role in the series finale helped bridge the gap between the show’s origins and its modern cast. A Worthy Farewell The two-hour series finale, , is frequently hailed

: As the new ER chief, Dr. Cate Banfield , Bassett brought a fresh, commanding energy to County General. Her character's mysterious past and eventually heartbreaking backstory added a layer of depth that many felt was missing in later seasons.