List what consecutive-season periods of various TV shows would you consider to be the show's "classic era" or "peak era".

That 70s show: the first three seasons was the show at it's prime. It was still good until Topher and Ashton left.

Bewitched: Darrin years

Bewitched: Darrin years

Do you mean Dick York years?

Yeah, they all were Darrin years.

Do you mean Dick York years?
Yeah I meant that

Cheers- seasons 6-9
MASH- seasons 2-4
Seinfeld- seasons 4&5
Frasier- seasons 2-4
Rseanne- seasons 2-4

MASH-seasons 1-3 (seasons 4-7 were so-so, season 8-11 were too preachy and dramatic, and too "Alda-heavy". Not to mention it over-stayed its welcome and should have been cancelled when Radar left)

ROESANNE-seasons 1-4

FRASIER-season 1 till whatever season it was that Niles and Daphne got together.

HAPPY DAYS-season 1, then they added that annoying live audience, some of the cast started shouting their lines, and it became "the Fonzie show".

LAVERNE & SHIRLEY-season 1 till whatever season it was they moved to Calif. and took half the town with them.

MASH-Seasons 3-7
Night Court-Seasons 3-6
Newhart-Seasons 3-5
Murphy Brown-Seasons 2-5

Cheers: Seasons 1-5
Roseanne: Seasons 1-6
Bewitched: the Dick York years
Diff'rent Strokes: the episodes until Dana Plato was fired
The Cosby Show: up until the "Cousin Pam" years
Friends: Seasons 1-4, until Ross became dumb and Monica became shrill
The Simpsons: Seasons 2-8
Happy Days: Seasons 1-2
Married... with Children: Seasons 1-5-ish
The Golden Girls: maybe all of it? I need to binge-watch to know for sure.
I Love Lucy: up until the move to Connecticut, although I still like the later episodes
Laverne and Shirley: up until the move to California
The Facts of Life: Seasons 1-4, although 5-6 had some great episodes, and 8 had three great ones, too

Sitcoms:
The Jeffersons - Seasons 4 thru 8
Cheers - Seasons 1 thru 5
Happy Days - Seasons 2 thru 8
One Day at the Time - Seasons 4 thru 7
Newhart - Seasons 3 thru 7
Three's Company - Seasons 2 thru 5
The Love Boat - Seasons 3 thru 6
Who's The Boss - Seasons 1 thru 6
Eight is Enough - Seasons 2 thru 4
Sanford & Son - Seasons 2 thru 6
Alice - Seasons 1 thru 4

Dramas:
Matlock - Seasons 1 thru 8
Emergency - Seasons 3 thru 6
Knight Rider - Seasons 3 & 4
Charlie's Angels - Seasons 1 thru 4
Adam 12 - Seasons 1 thru 5
Remington Steele - Seasons 1 thru 4
Batman - Seasons 1 & 2
Wonder Woman - Seasons 2 & 3
The Dukes of Hazzard - Seasons 1 thru 4
Dynasty - Seasons 1 thru 8

Game Shows:
Wheel Of Fortune(syndicated) - Seasons 1 thru 12
The Price is Right(Barker) - Seasons 1 thru 20
Love Connection(Woolery) - Seasons 2 thru 9