Ever bought a game and regretted it?

We've all had those moments when we're drawn in the by the stunning visuals, the seemingly too good to be true plot-line and the beauty of the characters. Instead of renting the game or asking for someone who owns the game's opinion, we purchase it. Only to find out that it falls horribly short of what we were led to believe.

I'm curious to know how many of us have experienced this occurrence, what game it was and what about it made it so bad?