I got the images from Wikipedia.
I liked ER a lot. Of course I liked George Clooney who played Doug Ross, but I actually liked Tony Edwards’ Mark Greene character better. I hung in there after George left the show; I pretty much stopped watching it after Tony left. Things weren’t the same without Mark Greene, although the rest of the cast was good.
Law & Order was the first and best of the Law & Order franchise, although I love the spin-offs too.
I think at least part of what made the original Law and Order special was that it focused on the cases the detectives caught, and left you wondering whether they would convict the bad guys or not. It wasn’t totally dependent on the detectives or district attorney’s office to carry the show, although the acting was great. Lenny Briscoe (Jerry Orbach) was my favorite character.
By contrast, the spins offs (Law & Order: SVU and Law and Order: Criminal Intent) did focus more on the characters, which made it hard when they started leaving. It wasn’t that the actors taking their place weren’t good; it’s just that the characters they replaced were tough acts to follow. It wasn’t the same when Chris Meloni left SVU and Vincent D’Onofrio left Criminal Intent. The relationship between Elliot and Olivia was central to SVU and the way Goren got the bad guys to confess was central to Criminal Intent. Good stuff.