I don't think that masses are dictating something. They believe what the media said and media says what was paid for. Most people believe in what they hear or read not too much on their experience. That is normal because today more people are playing games and the level is going down.
There are so many games which had excelentn first and second versions (or games) and then when companies grows they produced garbages. Look at Cossacks->American Conquest->Cossacks II; or Stronghold; or AOE 2 compared to AOE 3. Many good games were forgotten, no way to buy them, no mods, no new things, no working servers.
Companies are becoming larger and spent more money to do the same work with worse quality. Especially these tamagochies-free browser games called RTS...
Money is votes, and games which get the most money get voted the highest. Game companies which see their games earning lots of money will naturally assume that there's interest in a sequel. It's a safer bet to invest your money into a sequel for a popular game which already has an established player base than to invent a brand new IP. That's why we see a lot of companies making lots of version of Call of Duty, The Sims, Diablo, Halo, Deus Ex, etc. There is quite a bit of new and fresh content within the sequels (there has to be, or the sequel to the sequel will fail).
Note that if you're planning on releasing a new sequel or version every year or two, your next release is going to be competing with your current release. Every version of Microsoft Word is a very good word processor. Once you have a good word processor, why buy the next version? Keeping that in mind, would you intentionally leave out features from your current release so that you can include them in the next release? If yes, then your current release is slightly crappier. If you do it too much, you run the risk of gaining the reputation that your last release was crap. If you make the most perfect software you can possibly make, you can't release a subsequent version which improves on it, and thus are out of business. This might be a plausible explanation on why the quality goes down for franchises which have a monopoly on a segment of the market.