In that they created new storytelling structures, formats, or techniques that later became imitated and became the standard.

From what I have read, I Love Lucy was the show that revolutionized a lot of television。 First, the program was filmed with multiple cameras. They (I think Desi) came up with the ideas of selling the show to local markets in reruns. No one did that before.

The vast success of The Beverly Hillbillies surely accelerated the era of 60s high concept comedy. While it wasn't the first, it certainly set precedent for the decade to come.

How about Married with Children?

A family of losers that lead to other series about dysfunctional relationships (Roseanne, The Simpsons). I never met anyone who wanted Al or Peggy to be their parents.

When The Monkees debuted in 1966, it pioneered rock video 15 years before MTV first went on the air.

Boradly speaking, as far as I know these show reinvented their whole genre and pretty much became its blueprint.

The Simpsons for animation
Hill Street Blues for serious drama
My So-Called Life for teen drama
Star Trek for space opera

Then there are many smaller trends.
A few picks:
House: the main character was very popular and during its prime and in the following years many shows used the same type of protagonist.
Lost: also the excessive-mysteris series became a hit in mid 2000s, but unlike House no one was nearly as good.
Picket Fences: I think it created my most beloved subgenre; the light drama set in a small town with quirky characters. Or at least redefined. Many aspects were already introduced in Newhart.

The Tonight Show with Johnny Carson

It showed that people wanted to laugh late at night, leading to Saturday Night Live, which had Weekend Update, which led to The Daily Show. And all of the offshoots thereof...

Plus what it did for talk shows was almost inestimable

BROADWAY OPEN HOUSE


the first late night show on NBC that proved that audiences would watch TV late at night. Back then TV networks and local stations went off the air around midnight. It was thought that people wouldn't want to watch TV that late

For Dramedies I think both Frank's Place and Hooperman would fit this list. Yet perhaps the later years of MASH was one of the first.

Boradly speaking, as far as I know these show reinvented their whole genre and pretty much became its blueprint.

The Simpsons for animation.

The Flintstones was the first primetime adult cartoon. Granted the Simpsons did a better job at this. Based on the era the Flintstones were on they did as much as they could to be an "adult " cartoon.

Picket Fences: I think it created my most beloved subgenre; the light drama set in a small town with quirky characters. Or at least redefined. Many aspects were already introduced in Newhart.

Northern Exposure predated Picket Fences by two years (1990 vs 1992) and encompassed the quirky, small town subgenre.