If you sarcastically go around saying of new, terrible Broadway shows, "I laughed, I cried, it was better than Cats," there are (probably) a couple of reasons for that.
But one reason you say it is not because there was ever a real TV ad in which someone said those exact words.
Rather, a 1984/1985 local-to-NYC TV spot promoting Little Shop of Horrors off-Broadway seems to have been the genesis.
Featuring quick cuts of audience members extolling the virtues of the show — including a young woman deadpanning "it's better than Gremlins, better than E.T." — the show was immediately parodied by SNL via a sketch about a hypnotist (Jon Lovitz).
In the SNL skit, a succession of the Amazing Alexander's patrons drone, "I loved it. It was much better than Cats. I'm going to see it again and again" ... clearly under hypnosis.
In 1989, another spot captivated people's attention. In it, a woman named Paula is interviewed gushing about the then-new production of Grand Hotel, which was Cyd Charisse's Broadway debut (and in which Jane Krakowski appeared).
Her enthusiasm — "I’m going to see it twice more!" — has, over time, mixed in with the memories some people have of the Little Shop and SNL clips.
There is no replicating camp. It has to be this sincere. But SNL certainly lampooned it effectively, spawning a catchphrase in the process.