Dragon Age II...
I'm generally not easy to disappoint. Not because I'm cynical, but because I'm good at estimating the value of the games I buy. I keep up with gaming news and spend a lot of time thinking about how games work. So when my friends buy games and get disappointed, I'm usually the one who says "I told you so".
However, when it comes to Bioware, Rockstar and Bethesda, I admit that I do harbor some unhealthy optimism... But it didn't fucking matter because all the good things shown about DAII were true, it's just that they neglected to mention that it would be populated by cardboard cutouts. A lot of the gameplay ideas were pretty good, the cross class combos, the friendship vs rivalry in place of a binary like/hate bar. They weren't all handled well, but they were interesting. However, in the end, I couldn't bring myself to give a FUCK about ANY of my party members. They weren't just generic, they were one note. They all had one personality trait and a dark ambition or desire(Most of them didn't even have that, so they lacked in the most basic of character traits, motivation), that they recycled over and OVER, ad nauseom. Anyone that I started out liking I just got so fucking TIRED of.
They weren't so much characters as straw men held together with angst and "Witty" dialogue(Practically everything that came out of their mouths outside of dialogue was a joke). On top of that, the plot ranged from unfocused to non-existent(It only ever picked up in the last few hours, but that had more to do with my existing connection to the first game), the combat had some good ideas, but was garish and often repetitive, the side quests were predictable, and some of the voice acting was even a little sloppy.
Let me repeat that, BIOWARE, released a game, in which the VOICE ACTING, was less than stellar... THIS CANNOT HAPPEN.
The only time the game ever got a reaction from me was when I ran into my old party members from Origins and wished I could join with them and play as my Warden again...
So DAII is the only game I've ever played to make me sad by accident.