Just because you enjoy it doesn't make it good. I enjoy watching bad B-Movies for example.

If I enjoy it it's good enough for me

That I don't look at the time to see when it ends. If I can sit through it an not worry about the episode wrapping up or anything, then it's really enjoyable (I'm a person who obsessively checks the time, just a personality thing).

When it's not shit. I don't know any other way to describe it

For me I need a good plot, good characterisation and the style of either animation or acting has to look nice. I can watch stuff that doesn't match with this but I won't enjoy it as much.

So far only 3 shows have fit my criteria: CSI, Family Guy, and Primeval

I don't watch much sad stuff cause I don't like to cry if I can help it so I don't have much to recommend except the Walking Dead, but death becomes normal a few seasons in.

I couldn't get into it

That's fair, I stopped after season 3 I think. Sorry I can't think of any others to suggest

I stopped whenever Merle died

Wow that's early yeah

Interesting characters, interesting story, unpredictable (if each episode follows the same 20 minute basic outline then I'm out)
If it achieves a fitting mood and doesn't break a scene flow.

*every anime fan ever* Uh yeah, I watch it for the...plot.

That. I seriously cannot stand when shows de-value plot for....."plot" ya know.

Gotham is my fav recent show so far.
Same with The Good Place

Something gripping enough to catch my lingering attention. That or watching with others. I like a bit of suspense, but light touches of humor and reasonable storytelling can win me over. If it's flashy enough and doesn't flat line on action and movement, I'll watch it as long as it doens't offend my tastes.

saaame

Just needs to be interesting enough that I don't lose interest in it midway

Characters that I actual care about and invest in, otherwise it doesn't matter how well written the plot is, I don't really care.

Cool things need to happen