Bugs Bunny over all. That was the one you could count on always being on and the only one that I knew when it started.
The second most popular was Scooby Doo, but my brothers and I stopped watching it after they introduced Scrappy Doo.
After that, the most memorable was Schoolhouse Rock and the Time for Timer PSAs. I can still sing so many of those.
Others - whatever was on. I remember:
Superfriends, Fat Albert, Scooby Doo, Speed Buggy, Flintstones, Laff Olympics, Pink Panther, The Ant and the Aardvark, Hong Kong Phooey, Hair Bears, Tom & Jerry, Clue Club, Fang Face, He-Man, Blackstar, Space Ghost, Captain Caveman, The Herculoids, Thunder Cats, Voltron, Thundarr the Barbarian, Wheelie and the Chopper Bunch, Jabberjaw, Josie and the Pussycats, Wonder Bug.
Here's some obscure Saturday Morning shows I saw. None of them lasted very long, but when one stopped, something else replaced it:
The Ghost Busters (1975):
I was so young when I saw this that I had forgotten about it when the 1984 Ghostbusters movie came out. A decade later, I remembered this, and then had to convince myself that it actually existed. It took another solid decade for the internet to show anything on this.
The Monster Squad:
The Far Out Space Nuts:
Ark II:
Shazaam:
Isis:
https://youtu.be/FdBRLV6PGro
Electra Woman and Dyna Girl:
https://youtu.be/-9RqDx5qOe8
Land of the Lost:
https://youtu.be/n3m7Xow0YxE