Medal of Honor: Rising Sun. I was really into WWII games when this came out, namely the Medal of Honor: Allied Assault War Chest. It was my first WWII game for the XBox, and I was just thrilled when I got this game.
...and then I played it. Gameplay was stiff and lifeless, the guns sounded like they were spitting wads of rolled up paper instead of bullets, the AI was worse than ME, and I had the reaction time of a 12-year-old. The music was god-awful, which is just sad, seeing as how the music in Medal of Honor games are awesome, usually. The plot was hammy and had a boatload of unnecessary elements, including a cliffhanger that never got resolved. Overall, just a huge damn disappointment. I remember beating the game, and just sitting there, all sad.