For me it was Crysis. I had heard nothing but praise and glory for its amazing graphics and wonderful, open world gameplay. Within fifteen minutes I was bored, lost, stuck in a vehicle maint' pit and had a "sniper" shooting at me with deadly accuracy. OPKay, better find this sniper then, because this is getting old fast! So I try nineteen different ways to get out of the pit, the building and into the open, run from cover to cover and finally, FINALLY find the "sniper" firing through two windows of the building he is in, through a wooded area, through the window of the building I was in and into the pit. I make it up to where the "sniper" was, only to find it was a two man crew, facing backwards, firing a friggin' machine gun.
Seriously? They shouldn't have been able to even SEE me, let alone shoot at me through 50 obstacles with pin-point accuracy. Uninstalled and never went back.