Mass Effect 3.
The more I play it, the more I think that it's only one of my favorite games because of the two games behind it. The ending was not at all the biggest problem. Okay, maybe it was the BIGGEST, but it actually wasn't that bad in my opinion. It didn't even bother me at all the first time I went through the game.
No, the real problem is the myriad smaller issues. Some characters from the second game get real short shrift (Jack, Kasumi, Grunt, Zaeed). The lipsynching is sometimes pretty bad. The lack of a middle option in the dialogue wheel is definitely bullshit. Several choices from previous games are hand-waved or even dropped. The mission log is a joke, with no way to track your progress. The side missions themselves are mostly small, and far between, when they aren't simply boring fetch quests. Mordin has a different voice actor, for some reason.
But the biggest problem is, yes, the ending. But not just the last few minutes, no, it's the whole final mission. Whatever Bioware and EA claim, the game was rushed. The last mission shows it clearly. A lot of the areas in the game are interesting and cleverly layed out, with several strategies available to engage the enemy. The level design and cover system is better in 3 than either of the previous games, but the last mission is just uninspired. It's so small and linear, with no extra tricks and no choices to make like the Suicide Mission in 2. The entire setup is a joke, taking nothing into account aside from your Galactic Resource score slightly affecting the space battle cutscene. The whitewashing of previous choices my be forgiven, as I'm sure programming for all those contingencies was a total nightmare, but the final mission on Earth is shows none of the inspiration and none of the poish that the rest of the game has (as suspect as that polish may be.) It is much more disappointing to me than all the catalyst nonsense.
So much of this could have been better if the game were given another 6 months to develop. Bioware knew what they were doing, they were just not given the time and/or resources to accomplish what they planned. I know they can't be entirely to blame, but I know it was EA who caused most of the problems with ME3. They had oversight, they got to say what Bioware could do and what they to work with. They were the ones who were more concerned with a fucking release date than actual game quality. Fuck them. I want them to go away.
Not that I don't love this game. It's easy to overlook most of these problems for what the game does offer me. But it could have been Oh, So Much Better.