MMOs are far from being a new thing. We have been with them for nearly 20 years now. There are plenty of people out there that don't recall a world where MMOs did not exist.
Now the TV analogy... it is indeed close but not bullseye, not for every MMO. By definition an MMO does have a lot of work up front, years worth of production, 3 years is ideal but 6 years is not unheard off. By contrast, the amount of money you sink in subsequent content tends to be rather small.
TV shows do spend some up-front money for set-building but the up-front cost is not as disproportionate. Script writers and actors charge a LOT of money per episode. Even then, they market the show to the end, and not only in the station it's broadcasted. You see the show marketed in other stations that belong to the same network, in Hulu and Youtube via full video spots, over the web, on the radio, etc. They wont stop promoting a TV show until they cancel it, and even that last episode is heavily promoted.
As far as the MMO model goes, boxed expansions have worked for a long time. It may no longer work well, though. Ideally, even if we complained about it, CoH would have seen a yearly expansion, even if this meant thinner independent issues. Think of the expansions as the "episodes", or perhaps the seasons, of a TV show. They are great points for new players to jump in and well marketed content for those that did "everything" to return to. Yea we likely got that in the form of issues, but few outside the game knew about those issues.
I quit the game for a while after GR came out, and I didn't realize how many issues came out until I decided to return to the game. Social media may work, but it tends to work best at engaging current audience than spreading the voice (unless you give the followers something they feel motivated to share, something that has strong marketing punch behind it.)
Mind you: there were other things wrong with CoH. We got used to it over years and feel it as second nature, but the UI for CoH was horrible. Too many things all over the place, too many things hidden under layers and layers. Important features like the power inventory represented as a tiny un-searchable and un-categorized list of names. Movement was not exactly natural either out of the box. I got a few casual gamers to try the game and they had a very rough time getting around the interface and the controls. It is not very helpful to bring players in if there is such a high hurdle between the player and the game. I attempted to bring this up a few times but most players seemed extremely content about it.