Instead were cancelled because the network executives didn’t like it or the series were too expensive to produce?
I doubt it. The more popular the show, the more you can charge for the commercials, which will help you recoup your investment.
Sure! Deadwood & Rome.
I thought you were talking about commercial tv. I can see where good shows are cancelled on HBO, Cinemax, etc.
Wasn’t Rome only going to be two seasons anyway?
Bill Maher’s Politically Incorrect got cancelled for being, well, politically incorrect in the wake of 9/11.
Oh, and there was also CBS’s noted rural purge of 1971:
Several of the shows were getting good ratings at the time of cancellation.
Cheers was highly rated when it was cancelled. Production costs were cited as the reason for cancellation to the best of my recollection. (Hey, that was 14 years ago!)
Ahh, and here is a page that backs up my memory.
The Pretender and a couple of other Saturday night NBC series were canceled in 2000, despite decent ratings, because NBC thought they could do much better with XFL football on Saturdays. The executive who made that decision is sweeping floors in the NBC commissary.
Alien Nation was canceled by Fox. It’s ratings were good, and the network had told the producers it would be in the lineup up until the day the new lineup was announced. The reason appeared to be syndication rule: Fox owned the show, but wasn’t allowed to syndicate it (since they were trying to be a network, and networks weren’t allowed to syndicate at the time), so they didn’t want to make money for someone else (most drama shows make most of their money in syndication).
In both cases, higher ratings would have helped, but the ratings as they were would normally have justified renewal.
But that wasn’t a cancellation (i.e., the network canceled the show). The list of shows that ended because the production company decided to call it a day is quite long and includes The Dick Van Dyke Show, The Mary Tyler Moore Show, Everybody Loves Raymond, and Friends. The networks would have loved to have them all back another year or more.
If I remember correctly, Ted Danson decided not to return to Cheers because he wanted to spend more time with Whoopi Goldberg. They decided the series couldn’t continue without him.
Wasn’t the Smothers Brothers canceled because of a politcal comment? I don’t know what their ratings were. Also I think the new Star Trek show went of the air while it was still popular because it was a syndicated show and the network (Fox?) didn’t like it competing with its other new Star Trek shows.
You might be right about Rome.
I may be remembering wrong. My recollection was that cost was a major factor in the decision to end the series, which was part of the question asked in the OP.
IIRC, Rome was originally projected as a 5 year show.
It was, but the decision was made by Paramount, not NBC. Other high rated shows have ended their run due a decision by the producer or actors, but that’s not the same as a network canceling a show.
I could think of a few TV shows, but a radio station comes to mind first and foremost.
WKIE 92.7 FM used to be a dance station in Chicago. Before that it was Top 40 format (WKIS or “Kiss FM”). The guys who started Energy 92.7 had the great idea of doing dance without hip-hop or top 40 and the station had a huge following even despite its poor broadcast range. They beat out most every other radio market in the area with massive ratings. Problem was that the station’s parent company (Big City Radio) was in massive debt and was forced to auction off all its assets, including radio stations in Los Angeles, New York, and Chicago. Very disappointing. These days, the radio situation in Chicago is bleak. I think Spanish dominates more than half of the airwaves. Probably better than most of the stuff in English anyway, which is utter garbage. I only listen to AM anymore.
Or maybe I’m just getting old. 
Farscape was cancelled by the Sci-Fi Channel while it was still their highest-rated original show. Reasons they gave: the show cost too much to produce, and while ratings were high, they had declined slightly. Apparently, the thought process is, “If it stops growing, kill it.”
WKRP in Cincinnati was a Top 10 show when it got cancelled.
The producers of The Critic claim their show got cancelled merely because of one Fox executive who hated it. I suspect a little bitterness on their part, however…
Yeah, after the first statement the second one was obvious. 
It’s debatable, but one could make a case for Dark Angel.
Of which Star Trek show were you speaking? None of the Star Trek series ran on Fox. The Original Star Trek ran on NBC. Star Trek: The Next Generation and Deep Space Nine were both syndicated. Voyager and Enterprise ran on UPN. Only the original series and Enterprise were canceled by their network. And Deep Space Nine co-existed with TNG and Voyager quite happily for its entire seven season run, maintaining continuity with both of the other shows. (For example, Julian Bashir appearing in TNG or Q and Tom Riker showing up on DS9 as well as Dr. Louis Zimmerman, the creator of Voyager’s EMH.)
Enterprise was indeed canceled after its fourth season because of poor ratings.