It sounds more like you don't know how sales and majority polls works. See, the thing is, if 1000 people say they want X in a game, and bitch about it online, there might be double that amount of people who are fine with how things are, and don't feel like saying anything on the matter. They've got all they need. I don't understand how you factor sales into this idea either. See, if I buy a game, that decision does not mean I am happy with the content. And just because a lot of people buy Call of Duty, that doesn't mean Activision shouldn't think about moving their franchise forward, rather than cashing in on the status quo. I'm sure a lot of their fans agree with this as well - I mean, they too want new games in their favorite franchises to be good. But that doesn't mean they'll stop buying 'the same game every year'. Any fans have this issue, people keep buying Zelda-games even though they've more or less consistently been losing their charm. A sale does not mean that the buyer agrees with the content.
Looking past that, I think there's a bigger issue with the way you're thinking about this. Take the Mass Effect-ending problem. Some people were angry because they thought the ending was outright bad, and that they deserved better for their money. See, I've got a big problem with this. If you watch a movie and the plot takes you on a journey you don't fancy, for whatever reason, they okay, you don't like the movie. Maybe there's just one scene in the movie you didn't like, and the rest was great, but regardless, if you want your money back, or are prepared to ask the developer to change the ending because you didn't like it then I'm sorry, but you're an idiot. That's not how this works. You don't tell the author what to put in his book. You can critique his work and give tips on how books should be written, but you don't force him to write a story where the troll doesn't kill the girl in the end just because hey, you wanted a happy ending. That's up to the author.
Maybe you wanted say, a multiplayer feature in the latest game. But if including that goes against the values that the creators wanted to include in the game, then I don't think it's fair to fault them for not having it. I discussed the same thing with aaa2 a few weeks back, when he was talking about how he thought that games that didn't let players cheat was worse games, by default, compared to games that did. It's one thing to complain when a platforming game doesn't let you jump - but if the game does what it does without breaking apart, then that is not one of its low-points, and as a game critic, I would never fault a game for something like that. You can't really complain about a vision, but you can complain about a lack of one. My point is that you don't fault Call of Duty's gameplay for not having a rideable dinosaur. That would have been awesome, and it probably would have been a better game with it, but you can't rate something that isn't there. Am I making any sense?
The real problem behind the Mass Effect-ending however - the part of this post where I'm addressing you, Koh, is over. I just want to explain this thing because I brought it up - was that the developers promised one thing, then gave us something entirely different. When Mass Effect 1 was coming out, Bioware was saying that your choices in the game would echo throughout the trilogy, and that every player would not only get a very unique experience, but also that the ending would differ greatly from game to game. They followed through, mostly, but when it came to the ending, you were given three choices. A, B, or C. And regardless of which of these three you picked, you'd see a similar cutscene and then it'd all be over.
So the problem here wasn't really about the content, or the message of the ending(s), but rather with the mechanics - how it worked. Of course, causing an uproar over something like this is beyond silly, and I do not know what's wrong with the legions of fans who did that when it comes to Mass Effect. Though I think it is safe to say the ending sucked, regardless. 
@Shane: A game does not change over time, though people's opinions of what makes a good game does. Thus a good game back then might be considered a less worthy title today. Though to be honest, I think most games from before the 00's were pretty bad. There's a good reason for this, and it ties into what I just said: developers have, with time, learned how to use the medium to mold better experiences. Most of this 'moving the industry forward' has started happening with the indie-scene moving closer and closer to the front row. And that's funny, because the indie-developers are actually the developers today that are most like the ones we saw in the 80's and so on, in terms of how they work. It is just that today, they've got all that extra technology, but also a much better idea of what the gaming medium is.
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