Overlooked would have to be defined as at most 3 seasons, and never a popular show.
Bunheads is one of the best shows I have seen in years. Sad that it got dumped last month. Awesome dialogue and by the end the girls character development was wonderful. Made me go and watch Gilmore Girls for the first time, where I am on season 6 and loving it.
Rome is one of my favorite cable shows, but only lasted 2 seasons. Some great performances in that one.
Terriers, freaking great and a shame it got canned so fast
Shameless does not quite fit that definition, but no one ever talks about it and Emmy Rossum is fabulous in it. So much better than the original UK version.
There are some Brit shows that are amazing that were never that seen in the US that should be seen.
-Coupling is my favorite 30 minute show ever. IT is a bawdy friends.
-Utopia blew me away this spring. Can not wait for season 2.
-Life on Mars & Ashes to Ashes are a bit more well known, but other than the finale of Ashes were a great ride
-MI5 is 24 in London, without the time gimmick, and is great that any character can die at any time, and they do.
-Black Mirror is somewhat different in format than any current show (more twilight zone like), but it really makes you think and is done at a VERY high level of quality.
I have watched a lot of TV.....