Wow... I'm surprised to see how many people are listing actually decent games as the worst games they've ever played. It almost feels as if I alone has reached into the deepest, darkest parts of the abyss, while everyone else haven't even noticed the existence of it!
Before anyone go bashing and flaming, I know this is all very relative to the player, but I'm still very surprised.
Here are some of mine:
Necronomicon: The Dawning of Darkness
Horrible graphics made me want to poke my eyes out, sound hurt my ears, gameplay was incredibly slow, and story and characters completely uninteresting. Also, guy kills you after you knock on the door for no apparent reason? With absolutely no setup or explanation?
One of the few games I've started playing without completing.
The X-Files: The Game
Bad acting, very simple story, obvious bad guy, and a few really bad puzzles. What an insult to the X-Files franchise!
It's the basketball star in a fighting game á la Street Fighter... except that it sucks donkeyballs! The controls are bad, the story is bad, the concept is bad... It's bad!
Command & Conquer: Sole Survivor
Few have even heard of this game, despite being huge fans of the franchise. This was the only C&C game that wasn't included in the "The First Decade" collection. It's a multiplayer game with up to 51 players in one game. The graphics and top down view are the same as in C&C Gold. However, you only play as one single unit which you choose at the start of the game, and which you can't change unless you disconnect and connect to the game again. You run around picking up crates with various power ups, and then you try to kill your opponents.
The only time it was fun playing only one unit in any C&C game was when you had the Commando(or similar). This is as much of a fail as you get it. Also, it is impossible to play this game any other way than against NPCs now, because it relied on connecting to Westwood's official servers, which went down ages ago. And the AI in this game is pretty much impossible to beat.
Well, these are the worst ones I can come up with at the moment, but I'm sure I've played some that are even worse than some on this list... I'll post them if I remember them.