I remember Capitol Critters, I watched the episodes that aired. I never saw Fish Police except for the first episode I think. I do remember that the show was based on a comic book series that was much better than the cartoon turned out. Just a bit of the comic's noir styling got into the show, so it was a little more "mature" than the other series at that time, including The Simpsons. Maybe that's why it didn't take off. Never saw Family Dog.
The Family Dog series episodes failed to capture the anarchic spirit of the Amazing Stories episode that introduced it. The series was also a victim of poor timing; because of when it came around, people just saw Family Dog as another pale imitation of The Simpsons, when in fact Family Dog preceded The Simpsons.
I think the reason why Capitol Critters failed to catch on was because folks didn't know what to make of it; adults saw the cute little cartoon mice and assumed it was a kids' cartoon, and the subject matter of CC (the show tackled such issues as overpopulation, prejudice and gun violence, and the protagonist mouse's family was gassed to death by exterminators in the first episode) was a tad too dark for younger viewers.
I only saw the first episode of Fish Police; I never read the comic, but the show based on what I've seen was just a bunch of puns about fish.
Interestingly, even though "Fish Police" was supposed to be made by Hanna-Barbera, it doesn't even look OR sound like Hanna-Barbera made it. The animation and sound effects made it seem more like it could have been made at Film Roman or something (then again, this was during the time Hanna-Barbera was beginning to abandon everything that made them famous.) "Capitol Critters" was a tad better; the animation seemed like a typical 1990s H-B show, but the writing and several of the sound effects didn't seem much like Hanna-Barbera (it was WAY more controversial.) Unlike "Fish Police" though, "Capitol Critters" was co-produced by H-B and Steven Bochco Productions and distributed by 20th Century Fox Television (even at the end, it simply said "Produced in Association with HANNA-BARBERA, INC." followed by a custom animated Steven Bochco Producuctions (with a mouse playing the violin instead of the semi-animated photo of Bocho's violinist father) and the 20th Television logo.
I remember seeing all three. None of them were anything special. John Ritter was the lead voice in Fish Police. Neil Patrick Harris was the lead voice in Capitol Critters. Family Dog was kind of disturbing.