IMO they are entertaining but the quality varies between seasons.
I think theyre generally better than most of the Dc theatrical movies (Except Wonder Woman)
Flash and Arrow in S1 and S2 were great but their 3/4 seasons were mediocre or bad(Arrow S4)
Black Lightning is in its 1st season and despite me knowing nothing of the character , I really like it.
IT has a different vibe than the others because the main character is older and has kids and it doesnt really have a villain of the week feel that the others had starting out.
Legends was just ok in Season 1 , nd improved significantly in S2 imo.
They do have some cheesy elements but I Think overall theyre good.