Mr.K. said:
The ending is part of the package and if the package isn't good enough then damn right they can hate it.
And I highly doubt any game that was viewed negatively had "just a bad ending", fans and critics alike may use it as a quick escape got so the rest doesn't need to get talked about, but if a game left a bad taste in your mouth then the ending was just a tip of the iceberg.
I for one do not remember ME3, AC3 or Prototype2 being so great that only the ending can get bad marks.
If you want to live in blissful ignorance and imagine all the games you enjoy are perfect then by all means, but do not expect us to worship the same shrines you do and keep quite for the sake of your pristine bubble of happiness.
Pretty much what this guy said. Asking if you can hate a game because of its ending is like asking if you can hate a game because of a shitty interface, terrible controls, or broken aspects of gameplay. Its part of the whole product, and if its bad enough there is no reason not to hate it for that.
Also 100% agreed on the fact that it is never just a bad ending that causes problems. In the case of ME3 its what gets talked about the most thanks to how overwhelmingly bad it was, but even during the height of the Ending Phenomenon on BSN you'd still find at least 3 topics active to how terrible Kai Leng was, how the Thessia Mission was shit thanks to his plot armour, how they screwed up the Rachni, people not liking how Cerberus was handled, the masses of auto-dialogue and virtually every other complaint under the sun. At times it was a 50/50 split between Ending topics and non-ending topics, so people's problems weren't just with the ending.
Were it just the ending that had problems most people wouldn't really care - just skip the ending next playthrough. The rest of the game having problems is what causes people to stop playing and start complaining, it just so happens that a lot of those problems could have been fixed via the ending, but were arguably made worse instead.