Games usually have to grab me pretty quickly, or I just drop them, so I don't play a lot of unfun games for a long time.
Some exceptions were Final Fantasy 13, and to some extent the most of the Trails series (Trails in the Sky and Cold Steel).
Final Fantasy 13 I just tried a bunch of times, put in a combined 40h over the course of like three attempts, I don't know why, but it was just mediocre at best. During the final one last year, I made it about halfway through, and actually got turned off from gaming altogether for a few months. The story sucked, as well as the characters. I thought the combat could be interesting, even with the auto-battles, since you'd have to decide what "stance" your characters were in, but it was just lame for the most part.
The Trails series is a bit different. I actually liked the gameplay (turn-based JRPG combat is fun), but the story and especially the villains are just complete garbage. Two years ago, before Cold Steel 4 came out on PC, I sat down and played through all the games in like two months. While Trails in the Sky is trash, I was actually surprised to really, really like Zero and (to a little bit lesser extent) Azure. Those gave me hope, but Trails of Cold Steel just goes back to being terrible. I might still go back and play Cold Steel 4 and whatever other games continue or maybe finally finish the story, just because I've invested too much time at this point.