But as I started looking into it, there has actually been a pretty healthy number of shows based on comic strips as well. I could initially only recall Garfield and Friends and Boondocks. Later seasons of Garfield also featured U.S. Acres. And then I realized Filmation's Flash Gordon came from a strip originally too. And later Defenders of the Earth used Flash Gordon, Mandrake the Magician, and the Phantom as their protagonists. And then there was that Phantom 2040 cartoon. Popeye, too, debuted in comic strip form, despite being more well known through the cartoons.
And I started going through some old Saturday morning television line-ups. I was reminded that Heathcliff was made into a series, and briefly shared the spotlight with Marmaduke. And despite more recognition from the holiday specials, Peanuts had a series for a while too, as did Mother Goose and Grimm and Dennis the Menace.
But just as I was beginning to see that there were a LOT more comic strip cartoons than I realized, I also started being reminded of other comic book cartoons I had forgotten about. Men in Black, Sam and Max, The Mask, WildC.A.T.s, The Tick, Cadillacs and Dinosaurs, and Marsupilami all got Saturday morning cartoons in the 1990s. Not to mention some of the more popular shows from that decade like X-Men, Spider-Man, and however many shows spun off from Batman: The Animated Series. Sabrina the teenage witch even got her own cartoon! And that was just during the 1990s! As you get into the 2000s, there's multiple versions of the Ninja Turtles, Legion of the Super Heroes, another X-Men show, three more Spider-Man cartoons...
Oh, and let's not forget that we were getting more anime imports based off manga properties like Dragon Ball Z and Yu-Gi-Oh!
So without getting into a specific count, it does look like, at least in the last several decades, comic books have gotten more love in the world of cartoon TV series than comic strips. But, why?
Well, you can't tell from the titles, but look at the formats of the shows themselves. A lot of the comic book properties feature either a season-long narrative or at least each individual episode was a single story. Much like the serial comics they're based on. By contrast, most of the comic strip based shows run as a series of shorter vignettes. Normally, they'd run a little under ten minutes -- the length of time between commercial breaks. But some pieces, like the Garfield Quickies, were as short as only 30 seconds!
The comic strips, then, were based more on short-form storytelling and trying to drag out those out to a half-hour cartoon proved difficult. Fair enough, but why not take more advantange of the shorter, one story between-commercial-breaks format? Precisely because of those commercial breaks. From a marketing perspective, a television producer would ideally like to keep your eyes glued to the set for the full length of the program so that you see all the commercials. With the longer narratives, you need to hang around for the full show to get a complete story, so you have more incentive to keep your butt in the chair during breaks, lest you miss part of the show. But if you've got a complete story that starts and finishes between those breaks, you can safely get up without worrying about what happens next. And if you get up, you might not come back.
Now, whether there's any actual data to back up this idea, I don't know, but it's precisely the type of "everybody knows" information that a TV producer would base a lot of their decisions on. Never mind that the animation on Heathcliff was horrible, and the scripts weren't all that great, they would focus on the format, as that's more objectively quantifiable. So my guess is that the fewer comic strip cartoons than comic book cartoons we've seen over the years has more to do with a producer preference for longer narrative works that would (theoretically) hold a viewer's attention even through commercial breaks than anything inherent to the properities themselves.