As a semi-refreshing change from all the "Best game" threads that used to plage the forum, I offer up a different sorta poll- one that allows much refreshing whining, too.
The worst game I ever played would have to be... well, aside from the screechy-PC-speaker types that go beyond the beyonds and lock my computer as well, I'd have to say Nocturne. Only FPS I ever bought, had this wierd setup with cameras off in some corner so that as soon as you were attacked by, say, a horde of werewolves, you would immediately switch to a lovely view of, say, the main character's feet, which would shortly be joined by several of the main character's giblets.
A close second- whaddaya know, I just went and bought Outforce. It was worth the $1, but just for the cutscenes. The only "strategy" I've ever seen to actively encourage the tank (or, in this case, fighter/destroyer) rush.