I don't know really. Maybe COD4. Infinity Ward went from a great skillful game in online multiplayer in COD2, where the guns actually had recoil and you had to be able to use them, to a camping spray fest where cheap perks would get you to the top of the leaderboard and killstreak rewards which got you more cheap kills and encouraged more people to camp to get them in COD4. Then Modern Warfare 2 made it even worse.
Oh yeah and Prototype. I got it and the whole "Yeah I'm a badass" thing got old after half an hour, the story sucked, the side missions were repetititve, the main missions sucked, the enemies were cheap as fuck, the bosses were even cheaper, getting hit with rockets and falling every two seconds and then getting twenty strike packages on me sucked, the stealth sucked, the graphics sucked and just about everything else sucked. I traded it in for inFAMOUS as soon as I finished it. Best thing I ever did.
Soul Caliber 4. I was looking for a nice fighter I could get right into. I spent lots of time on the single player learning the moves. Then I went online and found that everyone just spammed Kilik or spammed the same move over and over with a character so I never played it again and bought Blazblue.
Assassin's Creed 1. I was so hyped up for this when I didn't have any current gen system and it looked amazing. I pretty much came into this gen because I heard about this game. I done the first assassination and thought it was great..........then realized you do that again eleven times in a row and never played it for months.
Brutal Legend. I played the demo and it seemed to be a full on action game with awesome music while cruising about the land of metal in your awesome car. Then I bought it off a friend and it started out as a nice hack and slasher, then I got some shitty watered down RTS fights for the rest of the damn game.
Fable 2, for the same reasons as you really. The jobs got soooooo boring, the game was short as fuck, the last boss sucked, the 'open world' was a linear corridor, the 'huge main city' was like three tiny areas seperated by loading screens, the combat was easy, the 'unrivaled NPC interaction' was just a minigame where you had to choose the right expression and spam it enough times so they'll mary you. I should've known Molneyeux was talking out of his ass again.