I don't really play the complete trainwreck games, because I would know beforehand that said games are complete trainwrecks. Even during ye olden days before the internet, I managed to avoid the real crap. Like, I know stuff like Superman 64 or Sonic '06 are terrible, but I never played them, so I can't count them. There's a couple that managed to slip through the cracks though;

Sim City Societies: What the h*ll was this? Floating stop signs? No realism? Zoning, power-lines, pipes, where are they? I already hated EA by the time this came out, but now they had blown it completely and permanently. Luckily I pirated this game, they weren't getting a cent from me.

Return of the King: Boring levels, boring gameplay, frustrating objectives, broken controls, EA on the cover... Lots to hate, way to ruin a great IP and movie. Luckily I got this one as a gift.

Star Wars Galaxies: Tried it out when it was free. Let's just say it reminded me why I hate MMO's pretty quickly.

A Bug's Life: At first it wasn't that bad, just your average movie tie-in game released in an age where 3D platformers were good, but then you get to the bird-boss and you notice how broken the controls are in this game. Borderline unplayable.

Wii Play: Well, who cared about this anyway, it came with the controller.

And to name something more high profile (though I guess Wii Play as already high profile enough in a way), a game that I actually thought would be good, but was a giant disappointment;

Assassin's Creed: I have never played anything more repetitive in my entire life. It's mind-boggling how non-interesting anything that goes on this game actually is.

I'm sure I played way worse games but Spectrobes on the DS comes quick to my head, maybe is because I had some expectations, but I think it was completely awfull.

Crash Team Racing on the Ps2 is another one, awfull, dissapointing and boring as hell.

Oh and the Ps1 version of Shadowman is one of the most disgusting things I have ever played, it made want to puke, is like if the whole world was a made of shit, the framerate was horrible, everything was ugly as fuck, the controls were clunky and the game was so damn boring and depressive... ahg I hate you for making me remind of that.

Superman on N64. It was just terrible and it was super expensive where I bought it (like 165DM or around 85€ and that in 1999).

Truly my worst purchase ever and that counts for everything I've ever bought...I was 15, that was a lot of money damn lol

Superman really hates me, my worst purchase ever had something to do with Superman and one of my worst cinema visits had something to do with him (BvS)

no idea, all the games i play are awesome

Some tiger electronics soccer game designed to look like a game boy.

Tie: Uncharted 1 & 2. I bought all 3 in a bargain bin about 6 months ago to see what all the hype was about. I didn't like anything about them and I couldn't be bothered to open up 3.

Oh, and Shadow of the Colossus. I wanted to like it because the big monsters looked cool and breathtaking. But the controls made it for one of my least enjoyable experiences I've ever had in gaming.

I sorta liked Qforce :-3

All 4 One was much worse. That was a turd.

Neverdead.
Loved the concepts and the designs. Slogged through the first level which was pretty shit but I figured it might get better. Start of the second level was somehow the worst designed section I've ever played in a video game.....

WHY? WHY WOULD YOU DO THAT!

Mine would be either that title or Infinite Undiscovery. 

Sonic colours was pretty badass if you ask me.