Wow...that's a hard one. For me, it's hard to pick shows that are still running, because they could blow it. Example: Lost. Now...I LOVE all six seasons of Lost, but for a lot of people, each season was worse than the previous one, and a LOT of people hated the final season. Currently, I love Big Bang Theory, Modern Family, Breaking Bad, Psych, and Dexter...but since they're all still on, they could ruin my love. Also...where would the BBC's current version of "Sherlock" fall? Each season is only three episodes, but each one is 90 minutes long...they're basically movies. SO...I'll stick to shows that are done.
30 min comedy = Scrubs. Only show that could make me laugh until I cried, and then just emotionally cry in the same 30-minute episode.
60 min show = Part of me wants to say Twin Peaks, but I'll go with The West Wing. I rewatched those this summer...so good.
With all of that said...the best thing I have ever watched on TV was actually a mini-series = Band of Brothers. BoB is hands-down the best program ever made.
I'm an English teacher...so I spend a lot of time in front of the TV grading essays