Re: Mass Effect 3
There are a lot of problems centered around Mass Effect's ending.
First, you have the problem of player expectations. In the previous two games, you could achieve a relatively happy ending, provided you put in your time, gathered as much side-quest support as you could, and made the best choices available to you. In the third, not so much. Therefore, the expectations the first two had created led to unfulfilled expectations in the third.
Additionally, the game advertised increased player responsibility in comparison to the previous games, games which were already seen as revolutionary in the diversity of their endings. The advertisements cited the staggering number of decisions from previous games that would carry over to the third, and stated that players would be able to have substantially different endings based on their decisions and actions. Those expectations were not met.
The ending itself was also a source of criticism, not only because of lack of player choice or because of the events themselves, but because of its incomplete nature. Love interests, major characters you've been with for years, whole planets and races - totally left out of the ending. It left the player sorely lacking for closure.
Finally, there was debate around the debate - criticism of the fan community for its outrage at the ending. A portion of the external media not only criticized the fan base for its 'sense of entitlement' but went on to cite the fan outrage as a major factor in why video games were not taken seriously as art - no artistic integrity in storytelling if the game is changed on behalf of fan outrage, and no fan support if it isn't. I believe Forbes had an article with this point of view that was particularly critical of the video game community, although it never really addresses the differences between movies and video games in storytelling.
So overall, it's really a question of which debate you want to take part in. How much freedom should the player be allowed in determining the ending of a video game like this? Does the community have a right to complain when an ending lacks depth, and how far does that right extend? Does the nature of video games allow for interaction between player and author, and subsequent development of the story (fleshing out vs. radical alteration), or does any change invalidate the artistic credibility of the game itself? At what point are the objections merely reflections of a sense of fan entitlement, and at what point are they legitimate criticisms of false advertising and failed promises? Is Bioware's publisher Electronic Arts really full of nothing but money-grubbing sadists bent on destroying the video game industry for its own sick pleasure?
Plenty of material for debate, and it'll be interesting to see how it plays out once the 'expanded ending' content is released this summer.