My vote goes to The Last of Us. It has already won hundresd of GOTY awards when I played it.
Or rather, tried to play it. I just couldn't believe that a game so mediocre received that much praise. I kept forcing myself to play some more every day, in hope it would get better. 10 days later, and some 8 hours of game time I finally gave up.
I was never more disappointed in a game, so much hype for nothing...