90% of Final Fantasy XIII.
Some of the boss fights were good and made good use of the battle system, I generally had fun running around and exploring the open-world section and taking on monster hunting sidequests, and there were some moments where I found myself getting at least a little interested in the story...
...but the vast majority of the experience was running down a linear corridor, fighting repetitive and disengaging battles, wondering when the plot was going to develop in an interesting and sensible direction.
No game has left more bored and disappointed, especially when you consider that I sunk 50+ hours into the game only to get an ending with no payoff.
It was only after the fact that I was told that I could get really into the story and make sense of the ending if I read the Datalog entries. So that's where all the fun in that game was? Reading on-screen text that explained the story rather than having the game story in those glossy cutscenes presented in a way that made sense?
(facepalm)