Final Fantasy I and II
and the original .hack quadrilogy
I always make sure to finish a game if I pick it up (which probably makes me a sucker), but man, those 6 games have probably taken me a year each to beat.
I wasn't expecting much from FF1, considering it's the first in a series, so I was expecting it to be, shall we say, sub-par for the rest of the series. I was right. It was flat, unfocused, and boring. Nothing exciting about it until the *very* end, and even that was a little bit of meh.
FF2's combat system killed me inside. I was just so frustrated with ability grinding all the time that I dropped the game from my radar for almost 8 months before I finally had the stomach to pick it back up.
Luckily, I played both of the above on the Final Fantasy Origins Playstation re-release, so at least I could pull up a world map. Without that, it probably would've taken longer.
The .hacks... Just the same thing, over and over and over and over and over, ad nauseum. The story was semi-interesting, but the amount of random fields and dungeons I had to do to get strong enough to continue the story killed all the joy for me. By the end of the series, it was a god-damned chore, and I was glad to be done with it. I played Bayonetta immediately afterwards in celebration.