Far Cry 2- had this preordered, hyped up by early reviews, yet as soon as I saw the user reviews, I sent it back sealed. Too many problems to even begin to spell out. Although it did show up a few gaming sites/PC magazines for giving high scores for early reviews.
Bioshock- seemingly loved by the console and PC crowd, I thought I'd also love this. Found the gameplay flawed (no penalty to dying???), controls felt awkward with a gamepad and KB/M. Seemed more like a game that should receive 80% reviews, not 95%!
Flashpoint 2. Like Farcry 2, another developer took up the mantle of producing it, and spectacularly messed up. Another classic of hype, big marketing budgets, but at the core was a poor console game. As testament to how bad it was, the developers stopped supporting it after a few months!
To a lesser point, Modern Warfare (1). Again hyped up by press and users alike. I thought it was okay, nothing more, and a massive step back from CoD:UO and CoD2.