Married With Children: Steve being replaced with Jefferson
Living Single: Synclaire and Overton marrying
New York Undercover: The Puerto Rican cop being killed off
Cheers: Diane being replaced by Rebbecca
The Cosby Show: the introduction of Raven Symone and later Erika Alexander
Roseanne: The original Becky leaving the show/David moving in.

Lost - The going back and forth in Time made me stop watching mid season last year.

Heroes - This show is supposed to be about Heroes and what they do for the world but all they ever do is battle each other and this caused me to stop watching season after a few episodes on season 3.

Desperate Housewives - Storylines dried up and I CAN'T STAND SUSAN!!!

American Idol - Having to watch a show that is on for over 4 months when it could be wrapped up in less time than that has me watching it maybe once a week.

The Dead Zone-New writers for the last season/death of Chris Bruno's character
Prey-ABC execs are idiots


I've drawn a blank on others right now

Law and Order: Every case becoming something federal, something involving the government, involving terrorists, blah blah blah.
Law and Order: SVU: I don't really know WHAT is it that killed this one for me, somewhere along the line of all these murders being committed in the squad room, that new cop in the first episode of the new season and the alcoholic ADA I wanted to see both of them die, having Kathy Lee on it as a lesbian that puts the moves on Olivia and Elliot, and bringing in Sharon Stone as Elliot's old partner and other new ADA.
Highlander: The red eyed demon crap and killing off Richie at the end of Season 5.
All That: Bringing in the new cast and doing away with Vital Information, Pierre Escargot, Miss Piddlin's cafeteria, Coach Creaton, Mavis and Cledus, Randy and Mandy, etc., and instead doing Harry Bladder and crap like that.
Are You Afraid of the Dark?: Not really killing it off, but the second series they did wasn't scary at all and the episodes were really corny. The first one was GREAT, but the second one were eeeeehhhhh.

Pushing Daisies - American audience is close-minded to quality television.
Traveler - DARN YOU ABC!

Melrose Place- Off the hook story lines, constant cast changing.

Supernova, that was Kathy Griffin. I loved that episode!

-

Without a Trace: It was cancelled so "Medium" could take its spot. That show had a lot left to give.

How I Met Your Mother: Absolutely no plot progression after the 4th season.

Family Guy: It's become a vehicle to pilot cartoon gore; cut-away gags are no longer clever.

The Simpsons: They've run out of ideas. Not a terrible show, but pretty boring in comparison to the first twelve seasons.

Will & Grace: Notoriously began repeating itself around season five. I got tired of the recycled jokes and love-lorn Will Truman (as if Eric McCormack wouldn't have been eaten alive at a gay bar).

The Cosby Show: I wouldn't say the series was ever killed, but as the children got older, they became less interesting. I'm glad they ended it on the note that they did.

Roseanne: Uh, they won the effing lottery. Terrible storyline. I'm glad Barr gave a nice middle finger to the people who ruined her show-- that series finale was AMAZING.

Brothers & Sisters: They took "SHOCKING TWISTS" way too far. It bordered on ridiculous beginning with the last season. Series finale was decent, though.

Daria: Nothing. It ended perfectly.

Six Feet Under: Ran on a bit long. The gimmick got older after the first few seasons. Again, had a strong closer, though.

Law & Order SVU: The announcement of Stabler's departure.

SCRUBS: This show will go down as being the most thoroughly destroyed sitcom in the history of sitcoms. The creators of this show will never be forgiven for that last joke of a season. It should have ended the season Zach Braff ORIGINALLY wanted to quit. That should have been it. Ugh.

I used to watch Days of Our Lives, but couldn't stand how long they carried on one storyline.

RedBedroom wrote:

I used to watch Days of Our Lives, but couldn't stand how long they carried on one storyline.

i used to be a days fan back in early 90's, i know EXACLTY what killed the show for me... when marlana got possessed!! Im a long time soap watcher, so i expect things to be kinda out there.. but that was too much for me. Havent watched the show since.

Two of them had run for 10 years and I think they were just running out of storylines - Touched by an Angel and Seventh Heaven.

One of them - Second Noah - I have no idea why it didn't last.

Third watch - I'm really not sure. I had 5 or 6 good years.

Days of our Lives - too much focus on the Dimeras and too many favs gone

AMC and GH and OLTL - my favs leaving or being written out and really bad writing

Others were just seasons - those summer series and stuff like that.

L.A. Law way back in the 90's: Final season episodes really jumped the shark.
Grey's Anatomy: Early in its season when George and the grieving blond doctor became a couple. It was a ridiculous set-up to me; also, I hated Isaiah Washington leaving the show.
Without a Trace: Simply got boring to me it its last couple of seaons.

And, while I am still a fan of 2-1/2 Men I really hated Charlie and Rose pairing up. But I think Charlie was getting a long in the tooth for the role.

Another one, I don't think I listed this before:

Homicide: Life on the Street - When they brought in Falsone and Ballard and Shepherd, and got rid of Kay, and Mike was thrown out for his part in the Mahoney shooting even though it WAS clean, and they keep that dumbass Falsone, the last couple seasons were just awful.

Project Runway: The gimmick got old. And then Bravo duplicated the formula for a million other shows.

Work Out: Jackie Warner comes off as an asshole. She wasn't fun to watch during the final season.

My Family - pairing abby with roger
Rescue Me - got tired of everyone's drunkeness