The one that became my "set aside all other activities for the night" was Northern Exposure, at least the first four seasons. It kind of fizzled the last two years or so when it was recast and the writers had run out of creativity. I liked it because it was unique, surprising, and full of characters with quirky, if not absurd personalities. A mix of stars, some unknowns. The odd thing, it was a hit, but never had a spin off or some other show that attempted to mimic it.
Also:
Dexter
Breaking Bad
Stargate SG1
Smallville
Downton Abbey
Queens Gambit
Evil