Some shows that had come to mind for me when thinking about the question include:
Stranger Things, which manages to keep me invested in all the characters, despite always splitting everyone up, and the situations in each season ramping up into greater ridiculousness. The worst I could say about a couple of the characters is that they're a little bland.
The Good Place is an especially excellent example of likeable characters, because the premise of the show is that the whole cast is terrible people who must grow and become better, and that's exactly what happens. It's like the opposite of what most sitcom characterizations end up being, which is either terrible people who remain terrible or get worse over time.
There are a couple other sitcoms I've really liked over the years that fall into that same diversion of standard premise.
My Name is Earl (and it's spiritual successor,
Raising Hope) start with archetypal "trashy" characters, but make the show about becoming better people. And, maybe the biggest surprise to me was
Broad City, where the typical group of insufferable urban hipsters are actually super empathetic and supportive of one another. Whenever I manage to find a show where it isn't an ensemble of 6-10 wisecracking sociopaths just behaving like total monsters to one another, I always hang onto them. I just don't understand why TV comedy especially relies on cruelty for laughs so often.
@Gruner, you make a good point about longer seasons vs. shorter seasons, and serialized vs. episodic narrative structure. I hadn't thought of that before, and I suppose all those approaches have their strengths and weaknesses. I definitely mostly find myself gravitating toward shorter seasons, especially for drama. It can even start feeling like a chore for me to hang in with 8 or 10 episodes, nevermind dozens. Episodic comedies have a bit more leeway, because they're designed to drop in and out of casually.
@rockin_rod Northern Exposure is one of my mom's favorite shows, and she watched it again recently. It holds up well, definitely owing a lot to an ensemble of a bunch of likeable characters. I will say that Fleischman's and O'Connell's unrelenting bickering can wear thin.
@Vixxen81 I wonder how the US version of
Ghosts compares to the BBC version? The US version seems very loud.