I definitely include Seinfeld, Star Trek (and its later versions), Miami Vice, CSI, Big Bang Theory, and I Love Lucy in this list. All of those shows have had gigantic success and reruns still air today, and in the case of Lucy, over 60 years after original airings. Even some young adults know about I Love Lucy, but unfortunately, not all of them.
I would also include Mork & Mindy...which introduced some guy named Robin Williams to the whole world. The rest was history, with Robin starring in tons of huge blockbuster movies making hundreds of millions, until his suicide in August 2014. That was very sad.
More to include: Bonanza, Three's Company, Law & Order, ER, and Everybody Loves Raymond. Again, those 5 were huge hits, and have been reran in syndication and on cable networks for years.
In my opinion, even game shows are iconic to some point: obviously Wheel of Fortune, Jeopardy!, and The Price is Right, but also counting on that list include What's My Line, I've Got a Secret, Let's Make a Deal, and Twenty-One (which sparked the quiz show scandals of the late 50s). The first three are practically American staples...everyone in America knows you can buy vowels on Wheel, answer in the form of a question on Jeopardy!, and win new cars and showcases on The Price is Right. The other four were 50s/60s smash hits, and one (Let's Make a Deal) is in it's 6th revamped season on CBS.