Nobody's mentioned the live-action
RoboCop: The Series yet. The same producers who made that went on to make
F/X: The Series, based on the Bryan Brown movies.
The Dukes of Hazzard was loosely based on a movie called
Moonrunners from the same creator.
The Universal Action Pack had a couple of segments based on Universal movies,
Midnight Run and
Bandit (based on the
Smokey and the Bandit movies).
...The Stargate director simply stopped after the first movie for some reason.
Actually Roland Emmerich and Dean Devlin have been trying to get a
Stargate sequel going for years. As stated, they sold the rights to MGM, which preferred to focus on the series; really, the movie didn't do that well at the box office or critically, so I guess there wasn't much incentive to do a sequel. But Emmerich and Devlin would certainly like to.
Just checked wikipedia and saw all those shows only last one season, though Alien Nation was reasonably successful because it had 5 tv movies each year after it end.
Alien Nation actually got good ratings, and the network wanted to keep it. But at the time, FOX was only broadcasting a few nights a week and wanted to expand its lineup, and they calculated that they could produce four sitcoms for the same price as this one expensive SF drama. So the show was cancelled for reasons that had nothing to do with the show itself. FOX and the producers worked together for years to find a way to bring the show back, because they all wanted it to continue, but it took about four years before they finally settled on the TV-movie revival.
It's not really a new practice, as some of the earliest television shows in the late 40s-early 50s were based on comics, radio shows, or movies. Superman and Blondie had appeared in all four mediums before 1955. The Blondie series starred Arthur Lake, who had been Dagwood in the movie series. One of the earliest genre TV series, Lights Out, was based on a popular radio anthology series by Arch Oboler.
Sometimes '50s and '60s shows used theatrical movies as pilots for TV series, back when the ratio of moviegoers to TV viewers was much higher than today. The '66
Batman movie was meant to be the debut of the series, but ABC decided to start the series early so the movie had to be postponed until after the first season.