Ahhh so many. And so many hours wasted. And these are only of top of my head.
Portal 2 - The puzzles were too easy , and after half or 2/3 of the game the tedious act of "finding the patch of wall you can shoot portals onto" was dull and repetitive.
Half-Life 2 - Didn't like it. Shooting buzzsaws at zombies in Ravenholm was fun, but the rest of it.. geez. The story was ... well not really presented at all to the player it was more of a "Go there! Go there! Go there" marathon. The citadel felt like a Xen rehash, including plattforming. And the G-Man's "BlahBlahBlah Mr.Freeman" left , probably not only me puzzled. After Half-Life 1 ah horrible downgrade
Talking about downgrades:
Crysis 2 - Yeah. Disappointing downgrade. Just forced through it to make space on my harddrive. Soundtrack was great though.
Duke Nukem Forever - Finished it just for Duke's sake. I hope it doesn't stand as the sad ending to the franchise.
BioShock - Serious mouse lag or mouse acceleration, I don't know what it was, but the gunplay was broken on PC. Aiming was completly botched up no matter if v-sync was active or not. Made me hate the whole experience. This and of course the hacking of safes, turrets, cameras, vending machines, security bots, toilets, fishtanks, rubberduckies...
Stalker - Hated it. Every second of it. Just rushed through at the end, ignoring side missions just trying to get rid of this game. AI was horrid, gunplay was unbalanced and monsters were overpowered. And the crashes... oh my god. I had a million of them with the game freezing and the sound going on a endless loop on a endless loop on a endless loop on a endless loop on a endless loop