It kind of varies from show to show. There are some that were really popular while they were airing, then quickly fizzled out of public conscious. Then on the opposite spectrum, you have the sleeper hits that were either initially dismissed, or completely overlooked, but enough word of mouth and memes caused people to look into it after it was already over.
Sometimes it's hard to predict what will or won't have lasting popularity, especially in a contemporary context. You'd be surprised at how many things were ridiculously popular when they were relevant, then quickly disappeared.